First, a few tips about the food culture in Rome. Although meals will be more expensive than you may be used to (depending on where you're from), bottles of delicious house wine can be had at any decent trattorie for less than the cost of a glass in the US. Also, take advantage of the free water fountains that exist throughout the city (no, we are not suggesting you guzzle from the Trevi Fountain; that is an entirely different type). Fill up a bottle to carry with you; the water is fresh and known to be totally safe. It is traditional to enjoy aperitifs (before dinner drinks) and hors d'oeuvres at many restaurants, while the ingestion of an expresso after dinner is a popular way of aiding digestion. Speaking of coffee, this culture is alive and well in Rome and has avoided the infiltration of international chains through a high quality local offering. Whether you are reposing in a popular piazza or delving off-of-the-beaten-path, cafes are everywhere.
Because you're in Italy, you'll want some pizza, which is offered as either a whole pie or al taglio (by the slice). Roman pizza is usually thin-crust, unlike the heartier pizzas originated in Naples. Avoid most shops in the touristy areas; they price gouge and the quality is usually lower. If they say “ENGLISH MENU,” turn the other way and walk a few streets to find where the locals go. Even if you don’t speak Italian, walk in with a smile and somebody in the restaurant will be sure to help you. Some places whose reputations precede them include Pizzarium (just west of the Vatican), La Montecarlo (across the Corso Vittorio Emanuele II from Campo de' Fiori), and Remo in Testaccio. Then again, three of the best pizza joints in Rome are within a block of each other across the Ponte Sisto in Trastevere: Dar Poeta, La Boccaccia, and Bir & Fud.
If you're serious on cultural immersion in Italy via your digestive system, then you'll want pasta. Although there are other cultures represented in Rome's dining scene (for cheap you go for Chinese), you'll want a crack at the selection of Italian restaurants available in all avenues of the city. There is a surprising number of excellent sit-down eateries south of city center in Testaccio, including the ultra-hip Porto Fluviale, the intimate Felice a Testaccio, and the local favorite Flavio al Velavevodetto (no English menu). There really isn't a heavy concentration of restaurants on any street in particular in central Rome; you'll instead find a scattering of quality past joints like Maccheroni tucked away on Piazza delle Coppelle, the delightful Roscioli on Via dei Giubbonari, and the classic La Carbonara (home of the original “egg and bacon pasta”) near Campo dei Fiori. Again, if you want consistently great food, you'll not find it as often as you'd like downtown. There are also some fantastic neighborhood restaurants in San Lorenzo, especially around Via degli Equi.
We cannot go without mentioning the ever-popular gelaterias. Quality will differ around Rome, but there are a few consistently excellent staples worth mentioning: Gelato di San Crispino near the Quirinal Palace, Giolitti a few blocks north of the Pantheon, and the seminal Palazzo del Freddo di Giovanni Fassi near the Manzoni station (great variety and inexpensive). There is also no shortage of gelato near Piazza Navone. If you are unsure, look for signs that say Produzione Propria or Nostra Produzione and you'll know that shop makes its own.
For further information on what to eat in Rome, take a look at our activity pages, talk with our community, or check out our related travel pictures and videos.