Paulie_D is totally right.
I also would like to add that at this moment, Michael strongly suspects Hyman Roth of the failed assassination attempt, coincidently just after a meeting with Frankie (refusing him to move against the Rosatos).
He is also checking Roth's reactions to see if he could get some tells. Maybe some reluctance would give Michael some doubts, but the fact that Roth accepts and wants to talk about something else confirm Michael's suspicions.
MICHAEL: The incident of the other night is
a nuisance that I can take care of. I came to you because I want nothing to affect our agreement; I wanted to clear everything I'm going to do with you, just in case.
He also flatters Roth.
MICHAEL: You're a great man, Mr. Roth, I have much to learn from you.
MICHAEL: Technically, they are still under the Clemenza wing of the Corleone Family, now run by Frankie Pentangeli. After Clemenza died, the Rosatos wanted territory of their own. Pentangeli refused, and came to me, asking for permission to eliminate them. I, of course, knew of their relationship with you, and in gratitude for your help with the Tropicana matter, turned him down. Pentangeli was furious, and paid one hundred and fifty thousand dollars to have me killed. I was lucky and he was stupid. I'll visit him soon.
All this aims to make Roth believe that Michael doesn't suspect him at all. Michael is still trying to figure out who sold him (he doesn't know about Fredo yet).