When you click on a Warrior in Roster Management, it prompts you to change his name. If you press ENTER without typing a name, the warrior is completely removed from your roster. The space is then free to sign another warrior. It does not appear that your Reputation takes a hit for doing this. My guess is that this is not by design.
On a similar note, I could not find a way to abort a name change. Perhaps pressing ENTER without typing in a name could act as the abort.
Chris