I've never actually started a cast from scratch, but I did take over and currently manage the Delaware cast, so hopefully I can be of some help.
You should have no issue with using RHPS assets on facebook or flyers. The worst that can happen is that FOX would say, "Hey, stop that", but it is such a small blip on the radar and in the long run would be making them money anyway. If you are going to use Rocky fan art please be sure to talk to the artist first to get permission. I've been pushing lately to stop the spread of uncredited art shared throughout the community.