Put roast, rib side down, in center of a 13 by 9-inch flameproof roasting pan and rub all over with 1 tablespoon oil. Press thyme to adhere. Season beef generously with salt and pepper.
Roast beef in middle of oven for 30 minutes. Remove beef from oven and with a bulb baster skim all but 1/2 cup fat from pan. Baste beef with fat remaining in pan.
Reduce oven temperature to 375 degrees. Roast beef 1 1/4 to 1 1/2 hours more, or until a meat thermometer inserted into the center of meat registers 115 degrees. Transfer beef to a platter, reserving pan juices. Let beef stand 25 minutes. (Meat will continue to cook reaching about 130 degrees for medium-rare.)