Players of the RTW take on the role of one of three Roman Factions in recreations of various campaigns fought in Ancient Rome covering the period of the Punic Wars to the rise of the Empire (approx. 270 BCE - 14CE). In controling the faction you manage on two levels: the Campagin and the Battle.
In Campaign mode you have an overview of the World (Mediterranean) and can send armies, diplomats, spies and assassins out to discover and conquer, liase, intrigue, and assasinate, respectively. You also have to manage the current affairs of your settlements by building and recruiting while managing your taxes and cash flow. Too few military in a town overburdened by taxes and under-serviced can lead to a revolt!
When one army comes up against another in campaign mode and attacks, you have the option to enter into Battle mode and command units of soldiers in real time using the Total War game mechanics. Attack a town or city and you begin to lay seige until the enemy sallies forth, or until they can no longer hold out and you knock down the gates to take the settlement. Following each battle, surviving units may gain experience. Generals can gain special abilities and occasionally attract retinue which add (or detract) from their individual abilities.
As the game progresses your family/faction tree will grow and you can begin to gain influence in the senate which gives those faction members additional abilities.
After finishing the game as a Roman faction, other non-Roman factions (former enemies) become playable factions, thus increasing replayability of the game.