01 - Preheat oven to 400°F.
02 - Pat the lamb leg dry. Using a sharp knife, make small, deep incisions all over the lamb. Insert slices of garlic and small sprigs of rosemary into the cuts.
03 - Rub the lamb with olive oil, salt, black pepper, chopped rosemary, and thyme, ensuring even coverage.
04 - Arrange the carrots, onions, and potatoes in a large roasting pan. Place the lamb leg on top of the vegetables.
05 - Pour the wine or broth into the pan around the lamb, not over it.
06 - Roast the lamb in the oven for 20 minutes.
07 - Reduce the oven temperature to 350°F and continue roasting for 1 hour 15 minutes for medium-rare, or until the internal temperature reaches 135°F.
08 - Remove the lamb from the oven, tent loosely with foil, and let rest for 20 minutes before carving.
09 - Serve slices of lamb with roasted vegetables and pan juices.