Some people here look at Rocco's volunteering for that "suicide" mission to kill Roth at the airport as expiation for his alleged role in the Tahoe shooting. That would fit in with Cristina's analysis. BUT:

In the sequencing of the film, Michael says to Tom, "...and then I'll know who the traitor in my family is..." The film immediately segues, bold and loud, to Fredo and that phone call from Johnny Ola. Then Michael, knowing that Roth was behind the shooting, goes to Cuba with only his bodyguard--literally into Roth's lair, the place where he knows Roth plans to have him killed--for one purpose: to find out who the traitor is. The traitor, of course, is Fredo. After he confirms Fredo and makes the attempt on Roth's life, there's no further emphasis on the Tahoe shooting--except for Michael to lure Fredo into his own lair and whack him.
Now, we know Michael never gives an enemy or traitor a pass. If Rocco had been part of the Tahoe plot, why didn't Michael whack him? You might argue that dispatching him on the "suicide" mission was Michael's vengeance, but I don't agree:
A subtheme of GFII [sound of plawrence groaning] is how Neri pushes past Rocco, and tries to push past Hagen, to become Michael's Number Two guy. Rocco is essentially reduced to being a glorified bodyguard in GFII while Neri participates in strategic discussions, business deals, etc. Neri was clearly more valuable to Michael than Rocco. So, in the penultimate boathouse scene, after Michael humiliates Tom ("...if history proves anything, it's that you can kill anyone"), he immediately says, "Rocco?" He doesn't say "Al?" because he needs Neri, but Rocco has become dispensable. Rocco volunteers, IMO, as a last-ditch effort to ingratiate himself with Michael and get back on equal footing with Neri-- not because he had a role in the Tahoe shooting.