Europa Universalis: Rome is a stand alone game based on the foundations of Europa Universalis III, taking you further back in time and allowing you to play from any date from around 280 B.C. to near the birth of Christ. Conquer the 'known world' as Rome or one of the other major states of the period or simply survive these growing empires as one of the smaller groups of people.
EU:Rome features an enhanced graphical engine over its predecessor, a smaller scope, and a number of tweaks specific for the time period. It is a grand strategy game that runs in "continuous time" (like most Paradox games), where the clock ticks away at the user's discretion, from paused to the passing of days within seconds. You control the overall guiding spirit of your chosen faction, developing your economy, military, infrastructure, and technology. War is handled on an operational level, with little direct involvement aside from making sure your armies are as large and prepared as necessary and your generals are the best choices for their situations. Games can be won on diplomacy, deception, and/or war, with the best results coming from balancing those actions and doing what's best for one's nation.
Taking a page from Crusader Kings, another Paradox game, EU:Rome incorporates some role playing elements as your nobles, politicians, and leaders are represented with detailed characters, each with their own histories and traits. They are born, seek fame and power, get married, win and lose battles, develop vices, and die. While you don't babysit a dynastic family as in Crusader Kings, you do get to watch and control as these various individuals develop friendships or hatred between them and, along with their various traits, these relationships can either make your country stronger or lead to an eventual civil war.