TB great post as always, but there is also another component to the visit to Miami. You are correct that Michael figured that Roth might conclude that he would realize that Frank Pentangeli was not the guilty party. Accordingly Michael was also steering Roth away from coming to such a realization. He deliberatley misleads Roth by asking his permission to kill Pentangeli, which is something he would do out of respect for Roth and to insure that Roth knew who did it, that there would not be a war over it, etc (with all the bad blood with the Rosatos and Frank, Roth would have needed Michael's assurance that the assassination of Pentangeli was a Corleone sanctioned operation so that "things" on the street would continue to run smoothly).