A couple of months ago we played a game with some of Adrian's ancient armies using a set of rules called Kings of War. These rules are a free download and are available from manticgames . Although written for fantasy battles, there are a number of free supplements at An Hour of Wolves & Shattered Shields.
for historical gaming, from Ancients through to ECW. We also used these for a Dark Age game using our Vikings and Saxons but I have no idea where the photos have gone! Sorry.