Are you running into a specific problem? Windows 2008 is supported with R2 and if you follow the deployment guides you should be fine.
There are a few configuraiton caveats, like this one for example:
http://blogs.pointbridge.com/Blogs/schertz_jeff/Pages/Post.aspx?_ID=64
Jeff Schertz, PointBridge | MVP | MCITP: Enterprise Messaging | MCTS: OCS