If you want a belly-filling meal visit this counter-serve deli, Food Factory, that has small batches of freshly made Italian or Mediterranean dishes ready for take-outs in cardboard boxes. They have a variety of vegan offerings too. Their homemade saucy portions of pasta and slices of pizza are yummy.
You can buy two 2 mains and 1 side in just 10 Euros. Depending on how much gluttonous you are this is sure to fill you up. Food Factory is comfortably placed in an open market of Piazza di S. Cosimato!