Can anyone explain to me what I need to change in order to prevent being able to login via ssh as 'root'?
By default, you *can't* log in via ssh as root. The only way you can enable root login via ssh is from the command line.
If you've done that (which I doubt), you need to undo it:
/sbin/e-smith/config setprop sshd PermitRootLogin no
/sbin/e-smith/signal-event remoteaccess-update