Heat oven to 325 degrees F. Combine rub ingredients; reserve 2 Tablespoons for potatoes. Press remaining rub onto beef roast.
Place roast on rack in shallow roasting pan. Insert ovenproof meat thermometer so tip is centered in thickest part of beef. Do not add water or cover. Roast in 325 degrees F. oven 1-1/2 to 1-3/4 hours for medium rare doneness. (Do not overcook.)
Meanwhile mix reserved rub with 2 teaspoons water; toss with potatoes. Roast in greased baking pan, covered, 1 hour. Stir potatoes; roast, uncovered, 10 to 15 minutes or until tender.
Remove roast when meat thermometer registers 135 degrees F. for medium rare. Let stand 15 minutes. (Temperature will rise to 145 degrees F. for medium rare.) Carve roast; season with salt. Serve with potatoes.