Found some discussion about this in the Super Group area so my question may be moot.
Virtue is the 'unofficial' RP server... but you'll find people and groups that RP pretty much anywhere.
"City of Heroes. April 27, 2004 - August 31, 2012. Obliterated not with a weapon of mass destruction, not by an all-powerful supervillain... but by a cold-hearted and cowardly corporate suck-up."
My as of yet small SG rolepleys their characters on Liberty almost totally. 
Pinnacle also has a large RP SG ring called the rp congress. I would say Freedom has very little from my own experience.
No other server beats Virtue in RP... not that I'm bragging or anything. Between Gemini Park, being invited to PUGs that RP, and people that RP at a Hami Raid I think no other server can beat Virtue.
Currently roleplaying, badgehunting, and laughing at the PvPers of CoX. lol, PvP.
Truedusk - Human Rogue
I am interested in finding out whcih server is the "role playing" server for CoH. I have seen many people post about their server being the RP server in the past but I cant find any of those posts now. So... any commentary is welcome.