I've had rotator problems in the past, but have been able to catch it early and fix it without surgery since we have an athletic trainer on staff at my command. He gave me some great moves which fixed me, and I now do as prevention/prehab.
All moves are done facedown on an adjustable bench, set to about a 45deg angle(give or take-not too low, not too high). Moves are done for 8 reps each, flowing directly into the next one after completing the reps for that move.
Y- either empty hands or with light weights(I've never used more than 8#), let arms hang straight toward floor, keep head neutral. Raise arms up until they are straight overhead, spread slightly out from straight up and down(thus the Y name). Pause for 1 sec, then lower back to start.
T- palms facing up, arms straight, raise arms straight out to sides until arms and body form a T. Pause 1 sec, then lower and repeat.
W- this one is hard to explain. Look in the mirror and hold your arms up so they form a W shape. Now, on the bench, start at the hang, then raise your arms directly into that position, try to hold for a second, then lower and repeat.
L- raise arms up tot he T position, but let forearms hang down from the elbow. Imagine a broomstick going from elbow to elbow across your shoulders, and keep the upper arms straight across. Rotate forearms up without moving upper arms, hold, then lower and repeat.
Like I said before, do 8 of the Ys, then go directly into the Ts, etc. until you have done all four moves for 8 reps each. That is one set, do 2-3 sets each time you do them, 2-3 times per week. I usually do internal and external rotations using the cable stack for 3 x 10, and then go to YTWLs.
Hope this helps.