Hard, salty Italian cheese made from sheep's milk, known for its sharp, tangy, and nutty flavor, often used grated over pasta, soups, and salads, or served on cheese boards. It's one of Italy's oldest cheeses, with a Protected Designation of Origin (PDO) status, meaning it must be produced in specific regions (Lazio, Sardinia, or Grosseto) using traditional methods, including dry salting. Its name means "sheep's cheese of Rome," and it's a key ingredient in classic Roman dishes like Cacio e Pepe and Carbonara.