/root/.ssh/authorized keys is not working - CentOS 6

We had issues on CentOS 6 getting the ssh keys working (/root/.ssh/id_rsa.pub copied to /root/.ssh/authorized_keys on remote box).
The keys worked fine for non-root users, but did not work for root.

The solution was found to run:

restorecon -R -v /root/.ssh

on the remote box.
Referenced from post #5