Sounds good Turnbull except:

When Pentangeli is about to be killed the Rosato bros. say "this is from Micheal Corleone" Later in the movie it's made clear that it was kind of a setup so that Pentangeli would think Micheal had tried to kill him. Why else would they have said that (this is from Micheal..) if they were going to actually kill him? Micheal didn't really have anything to do with the murder.

in other words, I felt the idea was that Roth wanted Pentangeli to think that Micheal was trying to have him killed so that Pentangeli would go to the FBI when the murder attempt failed.

When Tom Hagen tells Micheal that Pentangeli is still alive he says "Roth set the whole thing up" or something along those lines. The thing that doesn't make sense about that though, is that when the police officer comes in they all start shooting at each other, if it was just a ruse nobody would have gotten killed and the whole scene would have been faked to make Pentangeli think the police had intruded during the attempted murder. So then the question becomes: Who was in on it and who was not?