The Roman Magus was a powerful human wizard in ancient Rome and an advisor to Caesar Augustus, Rome's first Emperor (27 B.C. - A.D. 14). This "Original" Magus was the author of the Grimorum Arcanorum.  At Augustus' behest, and combining several magical artifacts to do it, in 10 A.D. he cast a Spell of Humility over the entire gargoyle species that caused their clothes to turn to stone with them during their stone sleep, a spell which lasts to this very day. 
The Roman Magus was the first person to combine the Grimorum Arcanorum with the Eye of Odin and the Phoenix Gate, a feat later repeated by the Archmage. He used these items to help cast the Spell of Humility. 
Presumably, the Roman Magus would appear in the TimeDancer spin-off at some point. 
When asked about the amazingly powerful Humility Spell, and how the Roman Magus was able to achieve it, Greg Weisman joked that he "must have had the backing of ALL of Rome's Standard's and Practice's Executives".