I'm not sure exactly how many adults there are lurking around, but I do know of many friends of mine that are 18+. Though, roleplaying with people should depend on their experience, maturity and rp skill, not age, if you'd like decent rp partners, in my opinion. I know someone close to me who is 14/15 but roleplays better than anyone I have ever met. Age shouldn't be a limit, but I do hope you find what you're looking for. I know the group I've been in for almost 5 years, The Ebon Circle/TEC, has mostly adults/mature-aged members. Might want to check us out, if you're looking for an active and long term group.