When a new roman name shows up in a text it will likely be their cognomen. Ex: Gaius Julius Caesar, would be Caesar. When you create the tag use the cognomen so this case would be CAES1. When you write the persName use the most common name the person is known by. So this case it would be Julius Caesar. If you don't know then simply use the nomen and the cognomen. In all case make sure to put their full name as an "aka".