In Centurion: Legionaries of Rome, players play scouts, spies, or special troops marching under the eagle of Rome. The book supports games in the Late Republic (from the Second Punic War to the rise of Gaius Marius), the Civil Wars (from Marius to Augustus), and the Principate (from Augustus to the Crisis of the Third Century), providing ideas for characters and adventures.
Characters are based around a collection of Qualities including a Concept (the central conceit around which the character is created, such as Seasoned Centurion, Illyrian Recruit, or Gallic Horseman), Traits (including Physical, Mental, and Social), and Elements (just about anything that describes a character, from "Farmer's Son" to "Swordplay" to "Cat's Paws.") which provide d6 with which one builds one's "hand" of dice (2d6 = 1d8, 4d6 = 1d10, etc) used in Tests, or task resolution.
This RPG is in the traditional style of having a GM prepare adventures and adjudicate the game, although there is some level of narrative control provided to players. This game works best with groups that trust each other and play in a cooperative rather than a competitive manner. If you need rules to protect players from GMs or GMs from players, this game is not for you.