From publisher blurb:
Raiders of the Republic is a campaign set in the Roman Federated Republic (RFR). The universe presented here is not is a parallel world where the Roman Republic happened in space. Although the history of the RFR does not match with our hostory, many names, places and events are parallels of their historical counterparts; however, there has been no effort to conform to historical events or biographies. This is fiction, not history, and liberties were taken to make the gaming universe interesting.
This campaign book is designed for use with the d20 MODERN Roleplaying Game by Wizards of the Coast under the terms of the Open Gaming License. However, the book is a self-contained universe description and the creative game master can adapt it to any Science Fiction RPG with minimal effort. In order to effectively use the material contained herein, it is recommended that copies of the d20 MODERN Roleplaying Game and d20 Future be available. The d20 Future Tech, Menace Manual, d20 Past and d20 Apocalypse books may also be useful, depending on the chosen campaign style, but are not essential.