I copied this from a UK wiki, but shouldn't link to it because it wants to download a trojan virus:
In the wake of Fidel Castro's takeover of Cuba in January 1959, Rosselli and other powerful mobsters like Sam Giancana and Carlos Marcello had worked closely with senior CIA officer William Harvey and others in the notorious CIA plot called Operation Mongoose, targeting Castro for assassination, which despite millions of dollars and several years spent, had ultimately failed. In 1963, singer Frank Sinatra had sponsored Roselli for membership in the exclusive Los Angeles Friar's Club. Soon after his acceptance, Roselli had organized and overseen a major card-cheating operation, one that had lasted four years and bilked scores of wealthy men (including millionaire Harry Karl, the husband of actress Debbie Reynolds) out of millions of dollars. In 1968, Roselli had been tried and convicted of illegal residence in the United States (he'd never acquired lawful US residence or citizenship) and had been ordered deported to Italy by the Immigration and Naturalization Service. Italy refused to accept him, so Rosselli remained in the United States.
In June 1975, Roselli had appeared before the U.S. Senate Select Committee on Intelligence led by Idaho Senator Frank Church to testify about his knowledge of and connections with the CIA's ill-fated Operation Mongoose. Shortly after Roselli had testified, the by-then disgraced former Chicago mob boss Sam Giancana had been shot and killed by an unknown assailant in the basement of his Oak Park, Illinois home days before he was to testify before that same committee, prompting Roselli (whose weakening power base had finally disappeared with Giancana's death) to permanently leave Los Angeles and Las Vegas for Miami. On August 9, 1976, Roselli's decomposing body was found in a 55-gallon steel fuel drum floating in Dumfounding Bay, Florida. He'd been strangled and stabbed, his legs had been sawed off and stuffed into an empty oil drum along with the rest of his body. Many believe Roselli had been ordered killed by Florida mob boss Santo Trafficante because Trafficante had believed the aging Roselli had talked too much about the Kennedy assassination and Castro murder plots during his Senate testimony.
Bill Bonnano states in his autobiography that while he was imprisoned with Roselli he spoke to him about the Kennedy assassination. Roselli claimed that he had fired a shot from a stormdrain located on Elm Street. Retrieved from "
http://dot cdo dot co dot uk/jfk/wiki/index.php?title=John_Roselli"