The hard part with the little muscles that make up the rotator cuff, is getting blood into them. They are hard little buggers to work properly, and it takes a fairly specialized set of exercises, in odd positions, to work them. They are easy to overload.
Light, light work, lots of repetitions with the exercises recommended by a good physiotherapist can really speed up the process. Regular shoulder muscle work, really does very little for the rotator cuff. The big muscles get all the work, and it can sometimes cause further issues.
Pay attention to the recommended routine for rehab, get lots of blood pumping through them so they heal and rebuild, and you will be golden.