01 - Preheat oven to 400°F.
02 - Pat lamb dry. Make small incisions throughout the meat and insert garlic slices.
03 - Combine rosemary, thyme, salt, pepper, olive oil, lemon zest, and juice in a bowl. Rub evenly over the lamb.
04 - Place onion, carrots, and celery in a large roasting pan to create a vegetable bed.
05 - Set the lamb on top of the vegetable bed in the roasting pan.
06 - Pour white wine or lamb stock into the pan.
07 - Roast for 1 hour 30 minutes for medium-rare, basting occasionally. For medium doneness, extend cooking by 15 minutes.
08 - Remove from oven, cover loosely with foil, and let rest for 15 to 20 minutes before carving.