I wanted to let you know there's a LGBTQ social group here, in case you want to re-post there, but this doesn't mean you're not welcome here though.

http://forums.psychcentral.com/group.php?groupid=24

I think you and your GF should have some nice discussions of how you feel and what you'll willing to do, to make her happy without sacrificing your own feelings. You probably equate rough intimacy as something mean and most do...but to someone who likes S&M this is exciting for them. Hopefully you both can compromise - best of luck.