Can you use Squad Leader from Dath Vader to give a free Action to a TIE Fighter that ended his turn on an asteroid so that he can Barrel Roll off the asteroid and there for letting him shoot in the combat round.

I think you can but wanted to be sure.

Also tryed out the 7 TIE Fighter + 1 named TIE Fighter set up and it was great.

Yes, you can. Overlapping (asteroid or ship) only causes you to skip that ships action(s), but does not prevent actions at other times. A stress token, on the other hand, would prevent it from being given a free action.