1Heat oven to 325ºF. Do not remove fell (paperlike covering) from lamb. Make 10 or 12 small slits in lamb with tip of knife. Insert slivers of garlic into slits. Mix remaining ingredients; rub over lamb.
2Place lamb, fat side up, on rack in shallow roasting pan. Insert meat thermometer so tip is in center of thickest part of lamb and does not touch bone or rest in fat. Do not add water.
3Roast uncovered to desired doneness: For medium-rare, 1 hour 40 minutes to 2 hours 5 minutes or until thermometer reads 140ºF; for medium, 2 hours 5 minutes to 2 hours 30 minutes or until thermometer reads 155ºF.
4Cover lamb with tent of aluminum foil and let stand 15 to 20 minutes. Temperature will continue to rise about 5ºF (to 145ºF for medium-rare; to 160º for medium) and lamb will be easier to carve as juices set up. Remove foil.