So here are some of the rooms I'm into that I enjoy hanging out in.
Nasty Shemale - First off, let me state my bias and say I have a bunch of friends in this room and am one of the many mods there. Anyways, this is a room that is active all times of the day, but the RP in room ranges from dirty cute posting all the way to actual RP. There are thematic trends in this room, right now I think were still in a busty boy phase.
Den of Depravity - Same sort of deal as the last room just without the mod status for me. I've found a lot of cool people in this place for private stuff, but the room itself is mostly a mixture of lewd posting and some light RP here and there. Has a decent amount of activity.
The other rooms I poke my head into are canon rooms, but the Touhou, Persona, and Danganronpa rooms seem to work for me.
I'd avoid Forced Breeding, has some of the most uptight rules, is not really an active room any more, and the mods there enforce "tumblr politics". Not worth the time, imo.