Sugo d'arrosto (Italian, "sauce of the roast") is an Italian term that simply means the "juice of a roast" - that is, pan drippings - made into a sauce. After roasting meat, the pan juices are deglazed with wine, enriched with butter or olive oil, and seasoned with garlic and herbs. The sauce is traditionally served with agnolotti but works well on any strongly-flavored pasta.
See also au jus, pan drippings.