I also play on AD and my best bet would perhaps be in one of the pubs, I guess that its either the old city one or the blue Reclusive that are the most crowded. That or you keep an eye out for a guild that might suit your taste. (I think AD should have like an RP-hub site but can't remember its name right now)
I myself is into the whole "Evil" RP and have had a bit of an issue with finding a guild suited for my taste since everyone either are some loyalist war guild or treehugging nature lovers. Though did have some luck and found a newly started Dark guild just the other week but we are really small at the moment and can't really go around recruiting in trade since that would go against the whole "low profile backstabbing evil worshiping bad guys" feeling we are going for
The easiest way on AD to find RP, is to join a guild saddenly.. Random RP is abit harder to come by, without Cathedral Square. It's always an option to become a travelling Smith/hunter/whatever and visit the Garrisons of the different military RP guilds, and offer them your services as a Smith, or simply sell some beer, skins or meat. That provides some nice RP