I roast a lot of meats in the oven and I add a little water to the pan underneath to prevent it from drying up, then with every temp check add a bit more as necessary. (Actually, I use a roasting pan with a rack to keep the meat out of the juices, and about a cup of water initially). When done, I've let the juices concentrate but not burn or dry up, remove the roast to a cutting serving tray, then pour the juices into a sauce pan, and add some water to the roasting pan and loosen the bits, then add it to the juices, doubling the volume to make gravy. I heat the gravy stock to a bubbling high, then turn it down and thicken it with a slurry of cornstarch and a small amount of water until it is a nice, smooth gravy. We don't add any butter unless there is insufficient fat to thicken, then add it sparingly, but normally we don't need to. And with a rib roast, there would be more than enough fat in it so it would not be needed. We don't add any salt at all and only a minimum of pepper, nothing else. I only use gravy sparingly on my potatoes, not on my meat or anything else. Of course I used to, I'd have a little mashed potatoes and meat with my boatload of gravy, lol, but no longer!
