This is a repeat of issue #132, but I also am getting an "unable to unlink" error when using Windows 7, Python 2.7 64 bit, and R 3.0.2.
Even trying to manually delete the file doesn't work as it is locked by a process. According to some unlocker software, it is locked by python.
In robject.py, I am able to confirm that the file is closed by inserting a print(tmpf.closed) after the tmpf.close() command. However, there must be a floating reference to the file somewhere (probably in the rpy2 C library code) that is causing this error.