During worldbuilding for a roleplaying campaign, I realized that I have a reasonable idea of what people have been growing (and eating) in northern Europe (rye, cabbage, turnips, beets and other roots, etc.), but my mental picture of what ancient Roman / Greek fields would typically yield is rather sketchy, beyond barley and olives...
Porcius Vitellius Cicero puts into the mouth of the elder Cato the statement that to the farmer the garden was a second meat supply.
Fruits. Besides the olive and the grape the apple pear plum and quince were either native to Italy or were introduced in prehistoric times.
Every fresh extension of Roman territory brought new fruits and nuts into Italy Among the last were the walnut hazelnut filbert almond and pistachio, the almond after Cato's time and the pistachio not until that of Tiberius.
...We read of artichokes, asparagus, beans, beets, cabbages, carrots, chicory, cucumbers, garlic, lentils, melons, onions, peas, the poppy, pumpkins, radishes and turnips to mention those only whose names are familiar to us all. It will be noticed however that the vegetables most highly prized by us perhaps the potato and tomato were not known to the Romans. Of those mentioned the oldest seem to have been the bean and the onion...
...Cato pronounced the cabbage the finest vegetable known and the turnip figures in the well known anecdote of Manius Curius.
Plants in great variety were cultivated for seasoning. The poppy was eaten with honey as a dessert or was sprinkled over bread in the oven. Anise, cumin, fennel, mint, and mustard were raised everywhere.
Meats. Besides the pork beef and mutton that we still use the Roman farmer had goatsflesh at his disposal and all these meats were sold in the towns. Goatsfiesh was considered the poorest of all and was used by the lower classes only.
...Pork was widely used by rich and poor alike and was considered the choicest of all domestic meats.
Fowl and Game. All the common domestic fowls chickens ducks geese and pigeons were used by the Romans for food and besides these the wealthy raised various sorts of wild fowl for the table in the game preserves... Among these were Romans for food and besides these the wealthy raised various sorts of wild fowl for the table in the game preserves that have been mentioned 145 Among these were cranes, grouse, partridges, snipe, thrushes, and woodcock. In Cicero's time the peacock was most highly esteemed having at the feast much the same place of honor as the turkey has with us... Wild animals were also bred for food in similar preserves the hare and the wild boar being the favorites.
Fish. ... in early times fish was not much used as food by the Romans. By the end of the Republic however tastes had changed and no article of food brought higher prices than the rarer sorts of fresh fish. Salt fish was exceedingly cheap and was imported in many forms from almost all the Mediterranean ports.
Cereals ...Of those now in use barley oats rye and wheat were known to the Romans, though rye was not cultivated and oats served only as feed for cattle Barley was not much used for it was thought to lack nutriment and therefore to be unfit for laborers...In classical times wheat was the staple grain grown for food not differing much from that which we use to day.
Sorry about the length(and OCR errors), but I did say the source was extensive...The book is a great read to learn about the Romans, and it does exist as a free eBook and on the web.
The basics would be the Mediterranian triad: Olives, wheat and grapes.
That does not mean that those were the only products cultivated, only the most important ones. I recall references to:
Other cereals as barley, rye and (in Eastern Mediterranean) rice
Lentils and other legumes
Fruits (not including oranges and other fruits introduced by Arabs and/or Crusaders about 1000 years ago).
As much fish as they could catch.
Apart from that, significant changes would be:
No rotation of crops nor fertilizers, which meant that after a harvest a field had to be left unproductive to replenish the nutrients.
The lack of large scale irrigation technology would have favoured the cultivation of crops that were less water demanding (which happen to be the ones of the Mediterranean triad).