Suppli are the Roman version of “arancini” — basically a croquette from cooked rice or pasta. The name, suppli, derives from the telephone cord because when you pull the two halves apart, the mozzarella should string out like a phone cord.
In the south in Naples, arancini are “mini” oranges and they are usually made of rice. In Rome, the suppli are often made with pasta. Suppli are smaller than arancini. They are greasy. As you can see in the photo, the suppli is not that big (it cost 2 euro because it was amatriciana — the normal one with mozzarella is 1.5 euro). The one that I got was a amatriciana, a pasta sauce made with guanciale (pork cheek bacon), cheese from Amatrice, and tomato sauce. The pasta in mine was tube pasta — like a straw.
Many appetizers in Rome involve something deep fried. These fried pasta or rice balls are very popular either as an appetizer or a snack. For some reason, always eaten with pizza. I don’t know why since I don’t associate pizzerias with deep fryers.