If the Roatos acted on their own to whack the caporegime of the top Mafia Don which wouldn't sit kindly with any Don
also it looks bad for Roth that his partner tried to kill Michael's partner when he went to make the deal, at his request
If, as I'm guessing, Roth told the Rosatos that Michael said, "Frank Pentangeli is a dead man," they'd regard that as a license to kill Pentangeli without regret from Michael. Since Michael sided with them on the Bronx territories, they'd see killing Pentangeli as logical and permissible.
I can't see Roth telling them that he was going to whack Michael in Havana and Michael still had his own men and there was plenty he could do to avenge the murder
Roth wouldn't need to tip his hand to the Rosatos--Havana had nothing to do with them. All they needed to know was that Michael said Pentangeli was a dead man, and that he'd be away from the US when they planned to whack Pentangeli.
The questions still lingering
1. Why would Clemenza make such a promise? What did Clemenza owe the Rosatos?
Doesn't matter to the storyline. ,
2. How can he promise these territories that are not his?
How do you know they weren't his (Clemenza's and later, Pentangeli's)?
3. Why even slippin' Michael didn't seem fazed
Do you mean, why didn't Michael seem fazed in Havana when he asked Roth, "Who had Frank Pentangeli killed?" If so: I believe that Michael regarded Pentangli as expendable. When he dispatched him to "settle these problems with the Rosato brothers," he was asking Frankie to put his head in the lion's mouth. If Frankie survived and settled the problems, so much the better for Michael--one less issue to trouble him. If Frankie was killed, more affirmation of Roth's perfidy. But, by the time of that scene in Roth's hotel room, Michael had already determined that Roth was a dead man.
