Just saw a museum on the Romans. Interesting stuff - they mentioned that Roman soldiers would normally eat as staples:- large amounts of porridge/grains - plus bacon, salt, vinegar and cheese. Upper-class Romans would also eat things like olives, dates, and seafood such as oysters and occasionally things like venison. They, generally speaking, were supposed to eat little meat as it was very expensive.
What surprises me is that half the children would die before the age of 6. I had always known that the Romans were very big on daily hygiene with their public baths everywhere. Does rather suggest that a poor diet, as opposed to bacterial contamination, was the real reason for the mass infections from plagues.