My opinion on the matter is that when Rocco was approached by Michael and told that he would do the hit in the airport, he knew Michael figured out he was a traitor because there was no possible escape from the bullets of "half the FBI" at the airport.
Now I think that you are reaching a bit.
I think Rocco must have known, as soon as Michael approached him to assign the Roth hit to him (a conversation which necessarily occured but is not shown on screen), that he was a dead man. Why? Tom already gives us the reason in the earlier "Difficult, not impossible" conversation: when Roth gets to the airport he'll be swarmed by customs and half of the FBI.
If that is the case than what benefit was it for Rocco to take the assignment? Why even bother showing up at the airport if you know that your boss is sending you on a suicide mission because he knows that you betrayed him?
With all due respect, your argument is weakening with each explaination that you give.
I don't even think Pentangelli's choice has to do with redemption, or going out with honor. It's a deal. Indeed this is how Tom puts it to Frankie. Frankie kills himself because he is getting something tangible in return: "When a plot against the emperor failed, their families were always given a chance to keep their fortunes."
Yes, it was a deal. But it was a deal presented to Pentangeli out of respect, out of understanding that he was duped into thinking that Michael tried to have him killed. A deal to let Frankie off the hook which allowed him to regain his family honor. A deal that said, "we understand why you almost testified against Michael, but it cannot be forgiven, so here is a way out with honor."
And Frankie took it to redeem his family's honor.
