Running R on OpenShift is easy, but not simple. You must install R as a user and tell python (rpy2) where to find it.
This repo includes R v2.15 compiled to run on RHEL 6.2 (base OS for OpenShift.com), as well as the OpenShift.com specific necessities.
WARNING: If you just close this repo and upload to OpenShift.com it will not work. There are a few more manual steps, see: README.Rinstall for tips.