I bought a book on rotator cuff rehab when I hurt mine doing ...drumroll... military press (taking it off the rack too far behind me, actually). There was only one exercise that seemed particularly useful for bodybuilders because of all of the other shoulder work we already do. It worked very well for me. I recovered in a couple of months (couldn't lift a towel over my head at first, and was back in the gym full-force after).
Lay on a bench, on your side. Hold a LIGHT (5-10 lbs, more is not better) dumbell in the hand that's on the top side. Rest your elbow on your hip and make sure you keep it there. Keeping your elbow at a 90 deg angle, slowly lower the dumbell to about bench level, then raise it up as far as you can comfortably. Repeat. Do a couple sets of maybe 10-15 for each arm, each workout. Increasing weight isn't really necessary, and beyond a certain point probably isn't good.
The exercise is called...external rotation, I believe. It works a particular small muscle in the rotator cuff that doesn't normally receive much attention.
The book mentioned a few exercises that everyone should remove from their workouts, due to particular stresses put on parts of the rotator cuff. One of those was upright rows (impingement of the shoulder ACL), and another was behind the neck presses (don't remember why, or maybe the list was too long).
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