01 - Preheat the oven to 400°F. Pat the lamb leg dry with paper towels.
02 - In a small bowl, mix olive oil, chopped rosemary, thyme, lemon zest, salt, and pepper until well combined.
03 - Using a sharp knife, make deep slits all over the lamb. Insert halved garlic cloves into the slits.
04 - Rub the herb mixture thoroughly over the lamb, ensuring even coverage on all sides.
05 - Arrange the onion slices, carrot chunks, and halved garlic bulb in a large roasting pan to create a bed for the lamb.
06 - Place the lamb leg on top of the vegetables. Pour wine or stock into the pan.
07 - Roast for 20 minutes at 400°F to develop a golden crust.
08 - Reduce oven temperature to 350°F. Continue roasting for 1 hour 10 minutes for medium-rare (internal temp 140°F), basting occasionally with pan juices.
09 - Remove lamb from oven, loosely cover with foil, and let rest for 15-20 minutes before carving to allow juices to redistribute.
10 - Carve the lamb into slices and serve with roasted vegetables and pan juices.