Cirencester Wargames has a set of modifications for the popular Lion Rampant games to allow you to play games set in Early Imperial Rome.
ancients
Warmaster Ancients Late Roman Counters
The League of Ordinary Gamers offers sets of print-and-play counters for playing Warmaster Ancients without the investment of time and money. Their latest is a set of counters for Late Romans.
Historicon Ancients Rules
Historicon is a set of free wargames rules for ancients miniatures. Alienstar Games bills it as a return the ancients games of old, featuring lots of figures, buckets of dice and army lists.
Munera Sine Missione Gladiator Rules
Munera Sine Missione is a set of free wargames rules for gladiatorial combat. Author Alan Saunders writes that these are:
Gladiatorial combat rules, using a hex grid. Simple armour and weapon categories make it easy to use your favourite figures, whilst a single bout plays to a conclusion in less than 15 minutes, making it suitable for campaign play in an evening.
Battle of Tanagra Board Game
The Battle of Tanagra board game recreates the battle of the First Peloponnesian War that was fought between the Spartans and Athenians.