One thing that was never clear to me was how did Michael know that it was Roth that tried to kill him at his home? (as he tells Frankie when he visits him in New York.)

By this point, it seemed as though it might have been Frankie based on the disagreement they had earlier that night...Roth and him were in on a big deal...Roth gave his approval in moving Klingman out.

So, obviously, Michael was right, but by this point in the film, what exactly told him that it was Roth? How was he so sure by the time he goes to Frankie?