I'll add another two cents to the "Why Rocco?" theory. Clearly Neri was the more favored of the two, and Rocco knew this. There has been a lot of speculation on the boards that Rocco did or failed to do something that irritated Michael. But there's another possibility. Michael knew that Rocco knew he was second bananna to Neri. Michael would also know that Rocco would be the most eager hit man to prove his loyalty exactly for that reason. Accordingly Michael "played" Rocco so he owuld volunteer for the suicide mision.

Not likely that an armed man who shot Roth in the airport Jack Ruby Style, and who was then escaping would end up anything but shot. Even if they had caught him alive, I doubt he'd break omerta, especially given the fact that he probably knew the way they would get to Frankie.