If you need a quality badass, Eric Roberts has always been your man. Witness his most recent role as a sadistic ex-CIA agent in The Expendables. He effortlessly injects class into the heroics – the mellifluous voice, the icy demeanour, the charismatic presence. So much so that Sylvester Stallone might rue his decision to kill him off, robbing us of the chance to see him in the impending sequel.

Roberts is also an interviewer's godsend. He's indiscreet, direct, very confident about his acting ability but modest about everything else. He claims he's not very intelligent and although that's belied by some of his answers, his talent is more instinctive than cerebral. And that explains his appeal. He's your regular blue collar type – the kind of guy you'd see at the ball game – the handsome but rugged features, the slightly slurred deep growling voice and the occasional descent into barrack room language mean he could belong on a building site.

He answers every question – but he's not always flattering about his peers or politicians. He has an opinion on everything. In fact, a news conference with Roberts is rather like a runaway train, the title of one of his best-known movies. We run the gamut as Roberts holds forth on politics, family life, his favourite directors and the economic mess in America. He hates George W Bush and conservative talk show host Rush Limbaugh, loves violence in movies – particularly those golden oldies made by Sam Peckinpah – sees it as his mission to save South America's rain forests and is not above being pricking the egos of a few of Hollywood's big names.  

Roberts is best friends with fellow badass Mickey Rourke (his co-star in The Pope of Greenwich Village) and Christopher Walken but he says we must thank Don Ameche (and what he claims is the old fellow's richly undeserved Oscar) for his prodigious output. (Wait for the story). He does not feign indifference when asked about his IMDB biography. He claims that all actors read their profiles. And – oh yes I remember now – he has a younger sister who has done quite well for herself in Hollywood too, and of whom he's very fond. 

If some of the above is a bit eccentric, then welcome to an audience with Eric Roberts. Well, what would you expect from a guy whose breakthrough role was playing Paul Snider in Star 80 (1983), the scumbag Svengali/husband/murderer of model Dorothy Stratten? That movie, directed by his idol, the phenomenally talented choreographer and dancer Bob Fosse (whose iconic movie was All That Jazz) launched him. Roberts has since carved out a lucrative career, mostly playing bad guys.

Sofia's studios
Roberts is in Sofia to film an Italian TV series, Honour and Respect, in which he plays a New York-based mafia boss. It's his fourth trip to Bulgaria but his schedule allows him to see little of the city besides the studio and his hotel. But he says that the facilities at Nu Boyana*, including the specially constructed New York back-lot in which late 1960s Manhattan was re-created – can rival anything offered by the likes of Universal studios.

Whether it's in Hollywood or Bulgaria, Roberts relishes playing bad guys.  

"I don't play imitations of bad guys like a caricature," he says. "After all, bad guys never think they're evil. They always think they're wonderful men. That's why I think I'm very good at it. I play them as if they're saints. Also they get the best clothes, the best cars and the sexiest women. And we get to die, so it's fun!"

Roberts has never been one to confuse his pay cheque with talent but he acknowledges that the true measure of an actor's stardom is their box office clout.  Nevertheless, some big names, he says, are lousy actors. The only name he will cite is Keanu Reeves. "He's not inspiring as an actor, except as an example of what not to do," says Roberts. He likes Sam Shepard and, perhaps surprisingly, John Travolta (set to appear in The Expendables 2). "I love John's work. He has never gotten his due. He's now doing a piece about John Gotti junior and maybe he'll win an Oscar."

On Julia
His younger sister, who has now charmed two generations of cinema-goers in the likes of Pretty Woman, Sleeping With The Enemy, Notting Hill, Erin Brockovich, and even enlivened the odd turkey (Eat, Pray, Love)  is, he says, one of his best friends and they correspond every day. They are both talented and charismatic, of course, but they share another quality; just as Eric is the rough diamond who coyly admits he's into poetry – the antithesis of the smoothness of, say, Jude Law – so his sister has something of the tomboy about her unlike, perhaps, the more refined Nicole Kidman. To that extent the siblings' chemistry is the same. He is immensely proud of Julia's success.

"I got her an agent and then three weeks later she got Pretty Woman," he says.

His daughter Emma Roberts, by a former relationship, is an up-and-coming singer and actress (she appeared with her aunty Julia in Valentine's Day) and fast becoming a star in her own right. Her new film, a high-school drama called The Art of Getting By in which she co-stars with Freddie Highmore, is due for release soon. Although Emma is only 20, he claims he never offers her advice.

"She's at an age where the last thing she wants to hear is advice from her father."

Roberts almost died in 1981 after a car crash. He was just 25.

"I had to teach myself how to walk and talk and remember again. All my short-term memory was obliterated. It was so bad that I'd brush my teeth, put down the toothbrush, rinse my mouth, and not remember where the toothbrush was. But I worked very hard, did a lot of crossword puzzles and physical therapy and, eight months later, I was doing Star 80 for Fosse. I became a more patient and kinder person. I understood I was mortal."  

Working with Fosse, who died in 1987 after a long history of heart trouble, is an experience he returns to throughout the news conference.

"On the first day we did a scene with me and Mariel (Hemingway). He said to her after one take 'what are you doing?' and she burst into tears. He turned to me and said 'I hope YOU can take it'. Fosse was one of the hardest, smartest, meanest, yet most compassionate people I've ever known. I loved him very much, he was an incredible human being."

Apart from Fosse, Roberts' favourite (older) director was the late Hal Ashby who directed the Vietnam movie Coming Home. Among younger filmmakers, he cites Phil Joanou who directed him, Richard Gere and Kim Basinger in Final Analysis (1992) and Jack Perez who directed him in La Cucaracha (1998) about a failed writer.

Roberts' recovery from the crash and subsequent success after a poverty-stricken background spurred him on to charity work.

"I'm involved in my charities because when you are successful it has a lot to do with circumstance, being at the right place at the right time. I've been very lucky all my life. I made more money than I ever dreamed I would make and I had more people who were kind to me than I ever dreamed of. I realised I could highlight things like animal abuse and child abuse. I have to give something back. If I didn't, I'd be a selfish bum."  If he has a credo, it's to treat children well. "If you never abused or humiliated a child there would be no war anywhere and that's probably the strongest, most profound truth to be said about mankind," he says.

On his 'hero' wife
Roberts appeared in his first play at the age of four and was in his first movie at 20. The film industry, he says, has now changed completely.

"All the major film studios and all the independent houses were run by businessmen who relied on artists to help them pick and choose. Now everything is run by lawyers. Was it Shakespeare who said kill all the lawyers? They're not artistic at all," he says.

Although Roberts' career probably peaked as an A-lister in the late 1980s he has always been a man in demand and enormously respected in the business. Mickey Rourke paid a memorable tribute to him when he won an award for The Wrestler. In his acceptance speech Rourke called for his friend to be given better roles.

"It was so heartfelt and it caught me off-guard completely. He and I are dear friends but I've never been more embarrassed in my whole life," says Roberts.

Talking of challenging roles, Roberts has just taken on a controversial part in The Child, a film about paedophilia, not normally a subject that sets box office tills ringing. It's close to his heart, however, because he and his wife, Eliza, work with abused children. One boy he befriended told him how he had been sexually abused every day between the ages of four and eight.

"I got very angry and very upset but I found out something incredibly tragic but true. Almost every paedophile was sexually abused as a child. It's not about sex; it's about domination. I realised that the world doesn't know about this. I thought it might be the first movie that deals with paedophilia for what it is, not just as a crime but as a crime that creates another crime. I hope it will be a wonderful movie."

Roberts describes his wife, who works alongside him in his charitable work, as his hero. "She's the best human being on this planet. She's a certifiable genius. Her father was a very famous writer, (screenwriter David Rayfiel) who died a few weeks ago, aged 86. I don't recommend marriage to anyone unless you marry my wife." His marriage, he says, is his biggest achievement.

Roberts always takes time for people, even though he admits it can sometimes be "a pain in the arse" to be interrupted at airports and restaurants. However, when fans approach him he remembers an incident in London from his days as a student at the Royal Academy of Dramatic Art (RADA).

"We drew straws to decide who would invite Olivier, who was doing Long Day's Journey Into Night on stage to our RADA production. Another student tried to speak to him but found himself speechless when Olivier exited the stage door. I went the next night and invited him. He put his arm round me, asked me my name and introduced me to his wife, Joan Plowright. That took just 20 seconds out of his life but I realised that was the closest I would ever get to him. So if he took 20 seconds for me, I can take 20 seconds for anybody."

On dark knights
Roberts had a small role in the recent Batman outing The Dark Knight. He remembers the late Heath Ledger fondly.

"One day we were on the set and doing a scene together when he suddenly turns to me and says 'how am I doing?' I said 'pretty well'. He was a normal guy. I was told all this crap about him, that he was unapproachable but in fact he was healthy, smart and sweet AND did his homework every night. I was very sad about what happened."

Perhaps surprisingly, Roberts claims that "six out of 10 actors do NOT do their homework" before coming on set. Hence it comes as no surprise, he says, that only about five per cent of actors have any career to speak of. He thinks that actors who claim they dislike learning lines too closely – because they believe their performance will lack spontaneity – are just excusing their laziness. Actors, he says, should learn their dialogue, say their cues and move the story on. Here, although he admires his friend Mickey Rourke (and as we have seen it's reciprocated) he gives an insight into why Rourke might not always have won a popularity contest with directors in the past.  

Every day on the set of The Pope of Greenwich Village (1984), Roberts says that Rourke would turn up late and improvise dialogue. Roberts, on the other hand, says he would keep rigidly to the script.

"There's a scene in the movie where I lose my thumb and I have a three-page monologue after a cue from Mickey's character. So I told him the night before, that he had to learn his lines to move the story on." Fortunately, Rourke obliged.

Just as he has little sympathy for ill-prepared actors, he believes that experienced stars should be able to avoid a Christian Bale moment in which the actor memorably ranted at a crew member who had been walking around the set during an important scene.

"I would have said to him: 'Christian, you're a good actor, just suck it in. Be here (in the scene); pretend you're not there. Simply, let's go to work.' Unfortunately, he'll never live that down," says Roberts.

Acting a storm
Roberts has a reputation – with 200 movies under his belt – for being a workaholic. Truth is, he loves acting and always looks for something good in a movie he's offered, whether it's the script, the location or the cast.  It was not always so. He changed his attitude after the 1985 Oscars.  Roberts was nominated for best supporting Oscar for Runaway Train. He thought that Klaus Maria Brandauer, who had also been brilliant in Mephisto, deserved to win for Out Of Africa.

To Roberts' disgust, the Oscar went to 77-year-old Don Ameche for Cocoon, whom he did not rate as an actor. Roberts says he was "heartbroken" but he decided then and there to take more roles and forget about awards. Among the "turkeys" he has done – and he admits to many – was a recent Roger Corman film called Sharktopus about an octopus shark in which he played a mad scientist.

"It was shot in Puerto Vallerta. I'd never worked with CGI before and so I got to learn this very hard technique and get paid for it. It's the worst movie on the planet but I had a great time making it. So you can thank Ameche for that."

Perhaps Roberts works so hard because of the ticking clock. He looks good for his age (55) and works out every day but his father, he reminds us, died when he was just 42. He says that in 10 years or so he will be an old man and the roles will dry up. "I love acting almost as much as I love my wife but I'm now on the home stretch. Jimmy Stewart and John Wayne hung in there into old age but they were the exception."

Acting, says Roberts, is just like sex. Everybody can do it but few can do it really well. Anybody can learn a few lines but few can really get into someone else's skin.

"When you start to get into a character's behaviour, you start to have real compassion for mankind. The hardest part I played was in Star 80. Snider was an arsehole but he was also a broken person, so when you saw him getting vulnerable, you felt compassion. I realised that even people you cannot abide probably have something to offer, so I love the characters I play, even Snider."

He says he does not feel himself to be in competition with other actors. "The great thing about being an actor is that there's nobody else like you. So you don't have to feel threatened."

Direction and other disasters
With a seemingly never ending list of credits and many other projects in the pipeline, according to IMDb (although he says that not all of them will materialise) he has no ambitions to branch out into direction. "I watch other actors who don't belong get behind the camera and try to direct. Or there are actors who direct one movie, get famous and then direct more and then you find out they didn't direct the original movie after all."

A proud liberal, Roberts was aghast at the Bush administration which, he says, wrecked his country. "You can't be a minority or a woman and be a Republican in the US. They don't talk about minorities; that's not an opinion, it's a matter of fact. Bush gave us Obama because he was a reaction to Bush, but here's the thing about Obama, he's not a liberal, he's a very conservative Democrat. Bush ruined our country economically for a generation, for 20 years. Talk to all the money guys. We're in deep trouble and it's because of his administration. We never elected him on either occasion; the oligarchy did. Hopefully because Obama got Osama he will be re-elected. Right now we have a Republican congress and a whole bunch of people who want to see him fail. Rush Limbaugh is an obese drug addict, a truly awful human being."

Poverty and hardship have been no stranger to the Roberts clan. Now, of course they are one of Hollywood's most successful dynasties but Eric has never forgotten the early struggles.

"If I hadn't got a scholarship I could never have gone to RADA. I could tell you terrible stories about growing up in poverty. We were so poor. Then, when I became successful, I rescued my sisters. Julia became the biggest star in the world. We were lucky in that we were able to take care of our other sister too."

Maybe one day Bulgaria's burgeoning film industry will lure his little sister to Bulgaria. We love you, Julia, especially if you're as delightful as Eric.

*Many thanks to Nu Boyana's Dona Doycheva who arranged this news conference