from the Introduction:
ADVENTURING IN IMPERIAL ROME
There are lots of opportunity for adventure in the later Roman Empire. Groups of men gather together to make their fortunes across the lawless Empire; as bodyguards, treasure-hunters and secret agents. These men are gladiators, deserters from the armies (who can't pay their troops), pirates, bandits, etc.
from the History section:
Roman Heroes is set in the Time of Chaos, from 235 to 285 AD. The fifty years following the death of emperor Alexander Severus were awash with assassinations, civil war, barbarian invasion and plague. Soldiers marched across the land in support of one claimant or another, treachery and adventure were everywhere. This is the real low point of the Roman Empire, and yet it is bursting with game possibilities and all the classic trappings of the Romans: gladiators, power-mad emperors, barbarians, a full complement of exotic provinces and eastern cults...
...Roman Heroes provides at best, conversion guidelines for the Fighting Fantasy rules and a host of campaign ideas. Detailed historical narratives of the Time of Chaos, and information on daily life is not provided. There are a zillion books out there that touch on everything from religion to sailing, warfare to villa architecture. In fact, the sheer volume of available source material was the main reason for choosing this period!