There might not be a playable Romulan faction in STO...yet...but there has been a Romulan Community in STO befor launch back in Feb. 2010!

If you would like to join Romulan enthusiasts, in discussion about everything and anything that makes a Romulan, discuss on Star Trek Romulan themed novels, and everything and anything Star Trek...this is the fleet for you!

http://romulanstarempire.com/home

And if you would like to know more about the Rihannsus known to the Feds as Romulans
here is a link to Rihannsu Encyclopedia.

http://www.pfrpg.org/RH/