Set in Europe at the time of the migration of nations (about 200-450 AD), Against Rome takes the player to that part of the continent that has not yet succumbed to the Roman Empire. This vast territory, which the Romans disparagingly called barbaricum, is the home of numerous primitive nations. The player takes control over one of these barbarian tribes, who as a whole stood out for a pronounced lack of cultural achievements, combined with a ferocious belligerence. Skirmishes, raids and plunderings were the order of the day for these barbarians and are, therefore, the great theme of this game.

Based in a small village, the player and his barbarians roam the vast forests of Germania or the barren steppes of eastern Europe to raid other settlements in their search for food, weapons and gold. These resources will help the barbarian chieftain expand his settlement and, above all, increase his reputation. While his tribe grows and flourishes, the leader obtains fame and experience and grows to be a master of warfare, until the player's barbarian empire is finally ready to take on the superpower of the time - the mighty Roman Empire and its apparently invincible army.