In Rome, there are supermercati and mercati. Supermercati are just like what you would expect, a supermarket that’s indoors with air conditioning and lots of packaged goods like you would find in the United States. Mercati are usually open-air markets or farmer markets with mostly local produce. This consists mainly of meats, cheese, and bread.

There are plenty of open markets and stores everywhere. All are super good and cheap! You’ll find it amazing to see the prices over here and they also give you moderate amounts at a time so nothing you can’t handle to finish! Plenty of butcher shops as well with local produce, whatever you prefer! Peanut butter is hard to come by, however, stores like Pewex have small amounts of it but can be expensive.
Tip at the supermercati or “grocery stores”. When you go to buy meat and cheese at the counter, they will either slice it up thick or thin, whichever you prefer. “Sottile” means thin and “spesso” means thick. Most of these workers will not speak English, so that’s very important to know! They also weigh by grams and anywhere from 100 to 300 grams will do just fine for meat, salami, cheese, etc.
Another tip is when you want to buy fruits or vegetables: you have to weigh them at the scale nearby, but before that, check the number written over the box (each fruit/vegetable has its own), then type the number on the scale.

Here is a link to plenty of supermarkets in the city center:  Exusemewhereis

Rome has some of the best markets in the world. A trip to a local market can be one of the best Roman experiences. These markets are generally open during the weekdays from 8 a.m. to 2:00 p.m. There are some that are open and only open on the weekends as well. These markets are a must if you plan on purchasing the BEST local products and the freshest fruits or vegetables. They also have clothes and other flea market goods, including original gifts you can take back home. Here’s a list of some of the best:

Mercato Campo de’ Fiori
Mercato Trionfale
Nuovo Mercato Esquilino
Mercato di Piazza San Cosimato
Mercato di Testaccio

Excerpting from Forbes Travel Guide, there are plenty of others too! Look up the best open-air markets in Rome and you’ll find lots of them.