Michael was almost 100% certain that Roth was behind the Tahoe shooting. His outburst at Frankie's home was designed to test Frankie's reaction, and then to soften him up so he'd agree to meet with the Rosato brothers.
I'm with this line of thinking. Every single move Michael made was cool and calculated, and designed to get others to do exactly what he wanted - even to get people to do things they really didn't want to do.
