I haven't done what you're trying.
Doing a web search using the following search terms resulted in a fair number of hits.
creating multiple build environments with chroot yum
The first one I see talks about doing this for CentOS which should be similar to RHEL:
However it shows that you do have to do a full install in each chroot as I indicated would be the case which is why I suggested VMs.
One idea might be to setup your chroot'ed user so that the myroot/etc/passwd gives him UID 0 so that when it logs in it is seen as the root user in the chroot itself. Or better yet setup sudo under the chroot (e.g. myroot/etc/sudoers) to allow the chrooted user to become root after loging. Since it is chroot'ed and logged into the chroot theoretically it should see myroot as / and only use anything it sees under that directory structure. I've not tried that myself though and there may be safeguards specifically to prevent chroot'ed user's from becoming root of which I am not aware.