"This requires the user names of new registrations to match the given regular expression."
Can I use this somehow to have the username NOT match a regular expression?
Or can I also use regex in the "disallowed text in user names" textarea.
There may be ways to write the regular expression to do what you want, though that will often be difficult. Otherwise, it would require some sort of add-on as the "disallowed text" option does not allow regular expressions.
