In a medium size bowl, combine garlic, rosemary, oil, salt and pepper together.
Rub all sides of the rack of lamb with the spice mixture. Cover it with plastic wrap, and marinate for at least 90 minutes.
Preheat the oven to 450°F. Roast rack of lamb for about 12 minutes. Turn on broiler to high and cook 5 minutes on high broil, or until internal temperature reaches desired doneness.