I'll go on record and say that Roth/Ola told Fredo to open the drapes so the assassins could get a clear look at what they were shooting. That they simply wanted to scare the hell outta Mike and not actually kill or injure him. Fredo believed them

Obviously Fredo did not kill the assassins, and here is where Rocco comes into this picture. http://www.gangsterbb.net/threads/ubbthr...ge=1#Post340717

EDIT #1--Roth wanted Mike to think it was Frankie who TRIED to whack him, thus Mike takes out Frankie saving Roth the trouble.

Also, the shooting scene has always baffled me. The assassin can see Mike and Mike sees him. Yet the assassin can't get a single shot at Mike? As Mike is crawling toward the bed 4 or 5 bullets hit the mirror directly above his head, and then then the fire curiously shifts away from Mike to above the headboard which seems strange since the assassin can see that MIke is clearly on the floor. Perhaps a very typical Hollywood device that we have seen in almost every movie made where the good guy narrowly dodges the bullets. Not likely in real life, but thats the movies. [EDIT]

(I will edit this post/theory from time to time )