So a couple of years ago I was looking for an herb rub for Prime Rib, and after combining a couple of recipes together I came up with this, but I can't tell you measurements or anything since I just kind of go by smell, feel, and color. :-) Helpful. I know. I've discovered that this is good on most roast, be it prime rib or whatever. If you want it really flavorful, I stabbed my roasts (prime rib) with knives and then put the rub on and then wrapped them in saran wrap and let them marinate for a day or so before cooking.
Dijon Mustard (Alot)
Beef Boullion (Alot)
Horseradish sauce (not the mayo kind, the REAL thing) (a little)
Onion Powder (or minced)
Garlic Powder (and if you want minced garlic)
I used it the other day on this sirloin tip roast, but I only had the cubed boullion so I stuck it in the water and not in the rub.