Does anyone else find it strange that Michael sent Rocco to whack Hyman Roth? He sent one of his top guys on what was essentially a suicide mission. Wasn't there a young button-man Michael could've gotten to do it. Just tell him some bs on how "if he does this he'll be a made man" or something like that, while knowing he might die. But Rocco?

I think it was for the same reason why Michael himself had to whack Sollozzo and McCluskey in Part I. Rocco was a caporegime in the family, and everyone KNEW he could get the job done. They couldn't take the chance that a rookie, even a very good one, might miss or not kill Roth. So it had to be Rocco, even though he probably knew his chances of coming out alive were slim to none.

One of the subthemes in GFII is how Neri tries to push past Rocco and Hagen to be Michael's #2 man. At Anthony's party, Rocco's like a rent-a-cop while Neri's in the boathouse waiting for Johnny Ola. Then Rocco's a go-fer: Michael dispatches him to feed Johnny Ola's men while he and Neri meet with Johnny (Rocco joins later). Rocco, not Neri, gets the s**t job of dragging drunken Deanna off the dance floor. After the attack, Rocco limps around trying to catch the attackers; Neri's probably sleeping. In the boathouse scene near the end, Rocco just stands mute while Neri, reclining in a chair, leads the discussion. And notice from Neri's sly look that he was the one who leaked to Michael about Tom's mistress and his employemen offer.
But, in the most revealing part of the scene: Michael says he wants Roth's plane "met." Hagen immediately says it's impossible to kill him in the airport. Michael humiliates Tom by saying that if history has taught anything, it's that anyone can be killed. Then he instantly turns and says, "Rocco?" Notice that he doesn't say "Al?" In effect, he gave Rocco no choice: either Rocco took on this likely suicidal task, or he'd be in the same doghouse as Hagen.

I believe that, by that time, Michael concluded that he didn't need two bodyguards. Rocco was expendible, Neri was more valuable. That's why he chose Rocco for this one-way mission.

I'm not gonna claim that this theory is the correct one, but you could look at it another way:

By asking Rocco if Roth could be killed, Michael may have been acording him more respect than Neri. By asking Rocco, the implication could be that Rocco was the more accomplished hitman, and Michael valued his opinion above Neri's.

At no time did Michael suggest that it had to be Rocco who actually carried out the hit. He was merely asking him if it could be accomplished. It was left up to Rocco to devise the method.

Had he implemented a different plan, other than one with himself as the shooter, and had it failed, Rocco could have always fallen back on his original "Difficult, not impossible" position.("Look, Mike, I tried. But Roth was just too well guarded. Even if I had gone on the hit myself, there was still no way ...")

I agree that Rocco saw his importance in the family diminishing with the rise of Neri, and I think he himself made the decision to be the assassin, figuring that (a)it had a better chance of success that way, and (b)by killing Roth himself, he could regain a measure of respect in Michael's eyes.

Turnbull? Neri was attempting to muscle Klingman out of the Hotel. So he couldn't have been there the night of the attempted hit on Mike.

I think Rocco should have taken so button men of his regime with him so he can carefully plan and succeed without getting caught.