Has Apple slipped in a recent change in the procedure to log in as root in Lion? (I'm using OS 10.7.4)
I went to log in as root to solve a problem with restoring a file from Time Machine (You do not have permission... error). As I have done in the past I used the method described in Apple support document HT1528 i.e. -System Preferences/Users & Groups/Login Items.... and found there was no longer a "Join" button in the lower right to click to get to Directory Utility to enable the root user account.
Anyway, after a bit of digging on the net, I found the Terminal commands to enable and disable root. Here they are courtesy of tekewin at Commandline Blogspot