Foods Not Known in Ancient Rome

Lemons were known from the 1st century AD, but not cultivated extensively.

Spinach and eggplant were not known until the 9th century.

No foods from the Americas:

• tomatoes (Solanum lycopersicum) is native to Mexico. The wild ancestor of cultivated tomatoes could be a kind of cherry tomato. Tomato was eaten by the Indians in the form of a sauce spiced with peppers.
• potatoes (Solanum tuberosum), despite their association with Ireland, were first cultivated by South American Indians in Bolivia, Peru and Chile.
• sweet potatoes (Ipomoea batatas) originated in Central America about 5,000 years ago 
• corn has been present since the dawn of time from Mexico to the Andes. Corn was the staple food of the South and Central American Indians.
• capsicum peppers, which include both hot peppers (chili, cayenne, paprika, etc.) and sweet peppers, are New World. Bell pepper is a variety of mild hot pepper that appeared in Southern Europe in the 18th century and was called sweet pepper. Peppers are all of the genus Capsicum, Solanaceae family.
• Some beans are New World, some Old World. Crosby lists "lima, sieva, Rangoon, Madagascar, butter, Burma, pole, curry, kidney, French, navy, haricot, snap, string, common, and frijole bean" as American, and mentions that soybeans are Old World. The author believes that broad beans, aka fava beans, are also old world. Black-eyed peas was the only bean type leguminous plant native to the Old World. It was already grown in Italy by the Romans and called Phasiolum. This pea, which is somewhat smaller than the seeds of the American variety of beans.
• The peanut is a legumuminous plant (Arachis hypogea) native to Mexico.
• The large Cucurbita genera are native to the Andes and Mesoamerica: cucurbita pepo, the pumpkin, summer squash, zucchini, and acorn squash comes from Mexico and the South of the United States; cucurbita maxima, Hubbard squash, comes from the mild climates of South America (Chile, Argentina, Peru, Bolivia); cucurbita moschata, butternut squash, comes from the Northwest of Colombia and Mexico.

Other foods not known in ancient Rome:

• Cucumbers originated in the foothills of the Himalayas in northern India, where they have been cultivated for more than 3,000 years. Iconographic and literary evidence has shown that cucumber was absent in Roman times, up to 500 CE, but present in Europe by late medieval times, 1300.

No pasta (introduced later)

Italian pizza might have its origins in Roman flatbreads and focaccia

Chocolate

Spinach and eggplant were not known until the 9th century. New World vegetables were not available: zucchinis, tomatoes, potatoes.