Y’know, I only recently learned about LJ/DW RP groups for other fandoms, but not ours. It’s not like that here in Tumblrland. Not as organized, which is both good and bad. Good because anyone can try, but bad because no one is obligated to RP with a new person.
I’ve been here in Tumblrland for a few years now, I’ve seen RPers come and go, I’ve seen VC RP directories born and abandoned, the RPers that are active at any given time tend to find each other and RP loosely. A thread here or there. Casual banter. That kind of thing. Because we all have Real Life, and that often interrupts more reliable/frequent (or longer) RP threads.
However, I would suggest you check out my tags below, you might find some active RPers that way. What you need to do is find an active RPer or two and peruse their archive, see who they interact with, and if you want to engage them, send them a private message and try to start a thread. You can also post RP memes, which you’ll find on other RPer’s archives. I think there are also tumblr blogs just for RP memes (starters and such for threads).
VC blogs/RP directories that may or may not be active, but you might find currently active RPers listed on them:
I-want-my-IWTV 