"Did the Rosatos try to kill Pentangeli because Pentangeli didn't appreciate their gesture of Goodwill?."

No. Their purpose was to kill Pentangeli:

Michael's last words to Roth in Miami were: :Frank Pentangeli is a dead man-you don't object?" Roth was the Rosatos' advocate with Michael, so he probably contacted them and said, "You heard about the shooting at Michael Corleone's place in Tahoe? Well, he knows Pentangeli was behind it. He told me that 'Frank Pentangeli is a dead man.'" He wouldn't have to "order" the Rosatos to whack Pentangeli--they'd see Roth's information as a green light to kill Pentangeli and not only to get their three territories in the Bronx, but also to take all of the Corleones' operation in NYC, too. Carpe diem. Roth also wouldn't have had to tell the Rosatos about his plan to have Michael killed in Havana--it had nothing to do with them.

Whether they sensed it or not, the Rosatos were part of Roth's grand plan: Inform them that they had the opportunity to take over Michael's "muscle" in NYC just before he had Michael killed in Havana. That way, the Corleone heirs would have no means to take revenge on him--a complete fait accompli. And, with Fredo's coglioni in his pocket, Roth would always have a hostage in whatever remained of the Corleone empire.