there are 2 excercises I mainly do for my rotator cuffs......hold your elbow to your side and bend your elbow like your holding a glass, but it should be a 5-10 pound dumbell. Now keeping your elbow in at your side bring the weight to your stomach and back beyond the starting position. The other one....hold your arms straight out your sides as if your a kid and your flying, now bend your elbow so your hand is facing up. with a 5 pound dumbell keeping that same position move the dumbell downwards and back up, rotating the shoulders. I do both to failure, rest 1-2 minutes and repeat 4-5 times and then do my regular shoulder workouts.
Hoe this helps...they do for me!