I apologize for the late response.
Runtime edition should be sufficient on your server if you only plan to build and run tests. R1 doesn't introduce any significant changes to Runtime edition (however, it does introduce changes in the way we distribute Qa and Dev edition). Take a look here for more details:
All the best,
the Telerik team
Do you think you know all the new features coming out in Test Studio R1 2011?
Think again - we have some surprises and will share them with you in the What's New in Test Studio R1 2011 Webinar on May 12th.