We dont have a formalized job description or policy, but great idea to consider. We do use SP's in our Mental Health sims, actually myself and my colleague are the patients. The course faculty assisted in our training, and we spent time observing in one of our facilities to enhance realism. Have been doing this for a year now and students really appreciate and are positive about this sim in particular.
We also have been doing multi patient simulation for over 2 years and again use SP's, faculty and non-faculty to support roles when needed. They are given specific info and scripts to follow to align with the objective of the sim, but as we all know, students can take you a different pathway than anticipated...they have become adept at ad libbing where needed.
Looking for others suggestions as well.