I don't think the Rosatos got away with it. According to Tom in the penultimate boathouse scene, Roth and the Rosatos were "on the run."

The critical word that confounds people (and prolongs the debate here, as dt reminds us) is "Roth, he engineered this one beautifully." Roth could not have engineered Frankie's survival via split-second-timed appearance of that beat cop. What he engineered, through Questadt, was keeping Pentangeli's survival secret; using Cicci as a stalking horse to testify that he never got a direct order from Michael (making Michael believe that he could get away with perjury--and then dropping Pentangeli on Michael, opening him up to five counts of perjury.

I've said before (though most here don't agree) that Geary was in on it. As a subcommittee member, he had to know that Pentangeli survived. He was the one who specifically asked Cicci if there were always "buffas" between Cicci and Michael, setting up Cicci's reply--"No, I never talked to him"--that made Michael confident that he could lie under oath.