Roman food - was painfully disappointing. And so because I can't say anything nice, I'll talk about tomatoes.
The best things in Rome, as in life, may not be free, but they can be very inexpensive. Purchased from the market in Campo de Fiori for a few euro, these little red gems called datterini (little dates) are sweeter than a bowl of M&Ms - and much better for you. So you can pop them down like pills all day long without guilt or regret.
Hard to imagine that something so identified with the food here were so scary to the Italians when they were first brought in from the New World - back in the days of Columbus. Thought to be poisonous, tomatoes were kept around solely for ornamental purposes. And then one day several hundred years later, one brave soul (no doubt intoxicated by that alluring fresh-tomato-in-the-garden smell) succumbed to temptation...and lived to digest it.
The rest, as they say, is culinary history.