How'd Michael know it was Roth? Roth undoubtedly wanted Michael dead soonest but blinded by revenge, Roth outsmarted himself with the Tahoe shooting plan and messed up big time!
You're still my brother Tahoe shooting “was a brilliant plan†with all the “moving parts†beautifully fell into place and the assassins right outside Michael's bedroom window with the drapes open, to machine gun spray such a confined space as a bedroom
The assassins had plenty of time too
1. Michael enters the bedroom
2. light is on
3. drapes are open
4. Michael spends time looking at the drawing Anthony had left him
5. Michael spends time talking to Kay who was already in bed
6. Michael stands by the window in full view of the assassins
7. Michael is silhouetted perfectly as an easy target
8. After all this time, assassins start spraying the bedroom with machine gun fire
9. Michael ducks, drops to the floor
10. Michael 'propels' himself on his stomach towards the bed
11. Michael pops his head up and pulls Kay down from the bed
Roth's best-laid plans....Yet the assassins still missed! Go figure!!