I will have to watch that scene again but as I remember, Ola's meeting was about moving Klingman out, not involving Roth's holdings in Havana and Rocco was not at that meeting He was feeding Ola's troops

It is Neri's job as Michael's bodyguard to be present by his side at all times, every meeting, every deal It does not imply that he is included in the deals or promised anything

If Michael had died everything dies with him and everyone none the wiser They came to know of Roth's tactics and Fredo's betrayal only because he survived