True enough TB. However, Michael's trip to see Roth must have been planned before the assassination attempt. Thus, there was no traitor at that point to ferret out.
Yes, I'm sure Michael had to set up some kind of meeting with Roth, prior to the shooting, so that Roth could introduce him to Batista and be blessed as Roth's successor. Perhaps he hadn't set up the date yet, or maybe that was one of the things he was discussing with Ola at Anthony's party. I'm
guessing that Michael rushed up the meeting right after the shooting to assure Roth that they were still good--and to hasten finding out who was the traitor.