Nice little food timeline here, although it would have been better with complete sources.
So… just introduced in 400 BC: beets – but just the leaves. Romans call it beta. Aristotle mentions the red variety the 4th Century, Theophrastus green ones.
Timeline says bananas were available, but the linked text says 3rd Century BC. Much smaller than today for sure, and plantain-like.
Peppercorn, garden cress, vinegar (the legions!) were already known. So were sausages, artichokes, etc. Great stuff.
Lots of foodstuffs came later and thus were not available to our 4th Century denizens: most shellfish (a shame), chestnuts, eggplant, omelets, etc. Of course, there’s always the possibility that some were already present but absent from the current historical record.
Further research: how was food prepared, especially cooked? What kind of ovens?