Roberts was born in Biloxi, Mississippi. His parents, Betty Lou (née Bredemus) and Walter Grady Roberts, one-time actors and playwrights, met while performing theatrical productions for the armed forces. They later co-founded the Atlanta Actors and Writers Workshop in Atlanta, Georgia. Roberts' mother filed for divorce in 1971 and it was finalized early in 1972. His younger siblings, Julia Roberts (from whom he was estranged until 2004) and Lisa Roberts Gillan, are also actors.
In 1972, his mother married Michael Motes, who was abusive and often unemployed. Motes had a daughter, Nancy Motes, who died February 9, 2014, at age 37, of an apparent drug overdose. Roberts' father died of cancer when he was 18. In 1983, his mother divorced Motes, citing cruelty and stating that marrying him was the biggest mistake of her life.
Roberts is of English, Scottish, Irish, Welsh, German, and Swedish descent.
Roberts's daughter Emma Roberts, with his then-girlfriend Kelly Cunningham, was born on February 10, 1991. Emma eventually became an actress as well, making her major-film debut at age 10 in the 2001 drama Blow.
On January 12, 2001, Roberts visited The Howard Stern Radio Show with his wife during a segment called "The Gossip Game" with Mike Walker of the National Enquirer. He confirmed that he and his sister Julia Roberts had been estranged for several years. The source of the estrangement had been his past drug abuse and her siding with his ex-girlfriend over the custody of his daughter, Emma. In 2004 he told People magazine that he and his sister were reconciled when he visited her in the hospital after she gave birth to twins.
Roberts is a vegan and supporter of animal rights.
Roberts got his start on the now-defunct NBC daytime soap opera Another World originating the role of Ted Bancroft from February 14, 1977, to June 17, 1977. Roberts received Golden Globe nominations for his early starring roles in King of the Gypsies (1978) and Star 80 (1983). He was nominated for the Academy Award for Best Supporting Actor in 1985 for his role as the escaped convict Buck in the film Runaway Train; the award went to Don Ameche in Cocoon. In 1987, he won the Theatre World Award for his Broadway debut performance in Burn This.
Roberts's other starring roles included Raggedy Man (1981), The Pope of Greenwich Village (1984), The Coca-Cola Kid (1985), Nobody's Fool (1986), Best of the Best (1989), By the Sword (1991), Best of the Best 2 (1993), The Immortals (1995), La Cucaracha (1998), Purgatory (1999), and Stiletto Dance (2001). He also had major supporting roles in the films Final Analysis (1992), The Specialist (1994), and Shannon's Rainbow (2009). He played the Archangel Michael in The Prophecy II (1997).
In 1996, he appeared in the Doctor Who Television film in the role of The Master (Doctor Who). As of 2011, he is the only American actor to play the role. When SFX listed previous Masters in Doctor Who, the magazine said of Roberts: "Out-acted by a CGI snake in the same production." In a darkly comic touch, the onscreen wife of Roberts' human character, who is killed by her newly possessed husband (who is taken over by the Master in the form of the above-mentioned CGI snake), is played by his real-life wife.
His recent projects include A Guide to Recognizing Your Saints, DOA: Dead or Alive and Royal Kill. He appeared in The Dark Knight as Sal Maroni, a Gotham City Mafia boss who hires The Joker to kill the titular superhero and a renegade mob accountant.
Roberts co-starred on the ABC situation comedy Less than Perfect. He appeared in an episode of CSI: Miami as Ken Kramer, a murderer on death row convicted of killing a young couple. Another notable TV appearance was the episode "Victims" of Law & Order: Special Victims Unit where he played Sam Winfield, a former cop turned vigilante. In the same year, he was also guest starred on The L Word as Gabriel McCutcheon, the father of Shane McCutcheon. In early January 2007, Roberts starred in the two-part mini-series Pandemic as the mayor of Los Angeles.
Roberts voiced the Superman villain Mongul in the animated series Justice League, and reprised his role in Justice League Unlimited in the episode "For the Man Who Has Everything". He performed the voice of Dark Danny in Nickelodeon's Danny Phantom. He appeared in the first season of Heroes as Thompson, an associate of Mr. Bennet. He then reprised the role in the third-season episode "Villains" and in the fourth-season "The Wall".
Roberts appeared in The Killers music video for their song "Mr. Brightside" and "Miss Atomic Bomb" as well as in the music videos for Mariah Carey's "We Belong Together" and "It's Like That". In 2006, he appeared in the video for Akon's "Smack That", featuring Eminem. In 2007, he appeared in the video for Godhead's "Hey You". He appeared as a panelist on the television game show Hollywood Squares. In February 2009, Oscar nominee Mickey Rourke, who starred with Roberts in The Pope of Greenwich Village, said he hoped that Roberts would soon be offered a role which would resurrect his career in the way that The Wrestler rejuvenated Rourke's.
He portrayed Seth Blanchard on the second season of the Starz series, Crash, from 2009. In 2009, Roberts appeared as himself in "Tree Trippers", a season five episode of Entourage. He is portrayed as a mushroom and drug fanatic as he gives the boys mushrooms and joins them to Joshua Tree National Park to trip as they contemplate Vince's next movie decision. It was announced in June 2010 that he would be joining the cast of the CBS soap opera The Young and the Restless starting July 12. In 2010, he appeared in the action film The Expendables. Later that year, he appeared alongside Steve Austin and Gary Daniels, his co-stars from The Expendables, in the 2010 action film Hunt to Kill. December 2010 saw the premiere of the fourth season of Celebrity Rehab with Dr. Drew, which documented Roberts' struggle with dependency on medical marijuana. Roberts starred in the 2012 mystery thriller Deadline, playing the role of politically incorrect reporter Ronnie Bullock. Roberts is also notably the first well-known actor to work with the youngest producer in history, Richard Switzer.