What I have been doing lately is adding some mobility work into my warm-up. Exactly what I do varies based on what muscle groups I am working on that day. On upper body days I will include some rotator cuff work in my warm-up.
They are not written specifically about the rotator cuff, but you should take a look at the Neanderthal No More articles on T-nation.
Part I
Part II
Part III
Part IV
Part V
I have been doing the complete Postural GPP routine, which includes a fair amount of shoulder work, once a week. You can find it in part IV, just above the exercise descriptions.
It is recommended in the article to do this routine 3 days a week. I'm sure Eric will have a better answer for you, but for me personally since I am doing many of the same exercises as part of my warm-up, I don't feel that it is necessary to do the entire routine more than once a week.