The method that djmsalem indicated has always worked very well for me on all types of beef roasts. One of the best. I prefer to reduce the heat down to 200 degrees F — as was suggested — and cook the meat very slowly. I would suggest a slightly alternate way to try (always using a good thermometer). That is to start out slow cooking a rib roast (or other beef roast) at 200 degrees F and then raising the temperature at the end rather than at the beginning of the cooking period. Alton Brown’s method (minus the strange clay pot that he suggests) is to cook at 225 degrees (or even lower) and then blasting it at a high temperature (450 to 500+) at the end for a few minutes. I’ve done some great prime rib roasts either way and while they both are good, the high temperature at the end seems to be best, at least for me. It’s turned out really well for me many times.