Sam "Ace" Rothstein is the protagonist villain of the 1995 crime film Casino. He's based off the real life Las Vegas casino executive and Mafia associate, the late Frank Lawrence "Lefty" Rosenthal.
Sam "Ace" Rothstein, a sports handicapper and Mafia associate, is sent to Las Vegas to run the Teamsters-funded Tangiers Casino on behalf of several Midwest Mob families. Taking advantage of lax gaming laws allowing him to work at the casino while his gaming license is still pending, Sam becomes the Tangiers' de facto boss and doubles the casino's profits, which are skimmed by the Mob before the records are reported to income tax agencies. Impressed with Sam's work, the bosses send Sam's friend, enforcer and caporegime Nicholas "Nicky" Santoro and his crew to protect Sam and the whole business. Nicky, however, begins to become more of a liability than an asset; his violent temper quickly gets him banned by the gaming board from every casino, and his name is placed in the black book. Nicky then gathers his own crew and begins running unsanctioned shakedowns and burglaries.
Sam, meanwhile, meets and falls in love with a hustler, Ginger McKenna. Despite Ginger's reluctance, they soon conceive a daughter, Amy, and marry. Their relationship begins to deteriorate when Sam and Nicky catch Ginger giving money to her former boyfriend, a con man named Lester Diamond. Sam also makes an enemy in Clark County Commissioner Pat Webb by firing Webb's son-in-law Donald Ward for incompetence, and refusing to reinstate him. Webb retaliates by pulling Sam's casino license application from the backlog, forcing Sam to have a license hearing, while secretly arranging for the gaming board and State Senator Harrison Roberts to reject the license. Sam responds by appearing on television and openly accuses the city government of corruption. The bosses, unappreciative of Sam's publicity, ask him to return home, but he stubbornly blames Nicky's reckless lawbreaking for his own problems. In a heated argument in the desert, Nicky chastises Sam to never "go over his head" again.
The bosses appoint Kansas City underboss Artie Piscano to oversee the skim and reduce the amount local mobsters are keeping for themselves, but he keeps incriminating ledgers and is caught on an FBI bug discussing the skim. Sam loses patience with Ginger after she and Lester are in Los Angeles with plans to run away to Europe with his daughter Amy. Sam talks Ginger into bringing Amy back, but Ginger's alcoholism and cocaine addiction anger him so much that he kicks her out of the house. She returns, on Sam's condition that she carry a beeper on her for Sam to contact her whenever he must. Ginger turns to Nicky for help in getting her share of her and Sam's money from the bank, and they begin an affair. Sam reaches his limit with Ginger when she ties Amy to her bed to have a night with Nicky. Sam confronts Ginger in the restaurant and disowns her. She turns to Nicky, but he has washed his hands of her as well. The next morning, Ginger goes to Sam's house, creates a disturbance, and uses the distraction to take the key to their bank deposit box. She takes some of the savings, but is then arrested by FBI agents.
With Ginger's arrest and the FBI's discovery of Piscano's records, which are then matched with the skimming operation, the casino empire crumbles and the bosses are arrested. During a meeting, they decide to eliminate anyone involved in order to keep them from testifying, including the head of the teamsters, the money courier, and several casino executives. Ginger dies nearly penniless in Los Angeles of a drug overdose, and Sam is almost killed in a botched car bombing, which he suspects Nicky planted. Before Sam can confront him, however, Nicky and his brother Dominick are murdered by Nicky's former associate, Frankie Marino (Vincent). Sam narrates that the bosses had finally had enough of Nicky, and had ordered Frankie to get rid of him.
With the Mob now out of power, the old casinos are purchased by big corporations and demolished to make way for gaudier gambling attractions financed by junk bonds. Sam laments that this new "family friendly" Las Vegas lacks the same kind of catering to the players as the older and, to his perception, classier Vegas he saw when he ran the Tangiers. In the final scene, an older Sam is shown living in San Diego, once again as a sports handicapper for the Mob, or in his words, "...right back where I started".