Paradigm Concepts' "Arcanis The World Of Shattered Empires" Has a very definate Roman feal to it. Admidittly the campaign is not set in Rome, but one of the dominate Empires is called the Coryani Empire.
The Coryani Empire has Strong ties to Rome. Complete with an Emperor, A Senate, Legions and Legionairs. There are detailed rules for Lorca Segmentata, Gladius, Pila, and Pugio. The Coryani Empire is one of several Empires in Arcanis, several of the other Empires have a definate historical basis. The Altherian Republic is an advanced Nubian Empire, the Theocracy of Canceri has a Babylonian feal, and there is Even an Egyptian Empire - The Myrantian's, (The Myrantian;s don't have a Current Goverment of their own, they are Currently a Protectorate of the Coryani Empire. There is More to Arcanis that just the Coryani Empire but it does play a major roll in the Settings Meta-Plot.
There are two essential books that are needed to play in Arcanis:
Codex Arcanis and the Players Guide to Arcanis.
Arcanis is also one of the RPGA's Living Campaings, but you do not have to be a member of the RPGA to play. But There are nearly 50 free Modules that are free to Download and Play For Members of the RPGA.
There are Several Websites Dedicated to Arcanis and A Lot of Yahoo Groups for the Living Arcanis Campaing.
The Main LA Yahoo Group is LA Talk
and the Best Arcanis Site is WWW. onaraonline.org.
Arcanis is a very Richly Detailed World and it is the best Romanesque campaing that I have found.