Ok...
Rocco's killing of Roth at the airport seemed like a suicide mission indeed; there was no elaborate escape plan.
Going back to Michael's conversation with Tom after Lake Tahoe's shooting; Michael states that all his people were businessmen, and that there lied their loyalties.

So how does a man who is categorized by his boss as de-facto a mercenary willingly go on a suicide mission?

As for Michael slipping; I never thought that he followed his father's style of leading the family; he did not hint - actually he was true to his military heritage... that scene where Tom was humiliated seemed very much like a military "situation room"; a General giving his Colonels their missions, and tolerating no one second guessing him.