How about the home dir of root that is /root/?
From some aspects, root is just another user (just better, and allowed more).
root has a home dir, but it is not like the other users in /home/,
but simply /root/ so root:s .bashrc is therefore /root/.bashrc
The ones in /etc is system specific settings for all users, including root.
Thanks to grawity to point out that you can use ~root points to the root home dir,
regardless of where it is.
You can test that with
$> echo ~root
So even thou /root will work on 99% on the systems out there ~root is probably more portable and will probably work on 100%.