Not quite sure why Apple added this utility, but dsenableroot appears to do just that, and only that. Simply do
% dsenableroot -u username [-p ] [-r ]Use a username that has administrative access to the computer. If you leave off the -p or -r switches, it will prompt you for these. Note that since any user with administrative priveledges can do this, you may wish to set your root password before someone else does!
Mac OS X Hints
http://hints.macworld.com/article.php?story=20031124001649938