We ended up here after wandering from Phillipsburg up Rock Creek Road. All campgrounds were full and we ended up driving for a long time until we reached Bitterroot Flat. Rock Creek is hard to access from the campsites and there is not much privacy. A neighboring campsite was shining a bright flashlight on our tent until dark.
Just as a warning, do not come here for fishing unless you are fly fishing. The water is really shallow and we lost around four hooks to the creek until we gave up.