For what it's worth, Tom says the following in the Second Draft of the GFII screenplay:

"Roth engineered it, Michael. He made Pentangeli think you hit him. Deliberately letting him get off alive. Then the New York detectives turned Frankie over to the FBI. My informants say he was half dead and scared stiff -- talking out loud that you had turned on him and tried to kill him. Anyway, they had him on possession, dealing in heroin, murder one and a lot more. There's no way we can get to him and you've opened yourself to five points of perjury."