[RF][Docs] Improve docs of RooMsgService.
[RF][Docs] Improve docs of RooMsgService.

root-mirror/root,olifre/root,root-mirror/root,root-mirror/root,olifre/root,root-mirror/root,root-mirror/root,olifre/root,root-mirror/root,olifre/root,root-mirror/root,root-mirror/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,root-mirror/root,olifre/root,olifre/root,root-mirror/root,root-mirror/root