All the classic rotator cuff exercises are good. You can do them with bands. You want to work internal as well as external rotation and work from a variety of angles. While doing the classic opening and closing the door ones with your arm at a 90 degree angle, squeeze a towel between your elbow and your body. This will help you maintain the correct alignment but will also strengthen the RC muscles as a whole in their task of keeping the head of the humerus bone securely in the socket- which is precisely your goal.
Look on YouTube for exercises. You'll find tons. Or come work with me! It's important that your shoulders, head and spine are aligned correctly for them to be effective. If there are issues with that you may need to work on those things first, or at least understand how to do it all at once.
Good luck! Hope this helps.
