RP becomes much more difficult in RTS's; not to mention that the genre itself doesn't really go out of its way to promote it like RPG's do. I suspect light RP will be common enough in chat that you can pull that off but you wont find the walls of text and stories the way you would in other games that support it. Anyways, if it comes down to it I'll roleplay with you, we'll find each other in-game. We roleplayers got to stick together!
No problem can stand the assault of sustained thinking. - Voltaire