Preheat the oven to 325°F (165°C).

In a bowl, mix together garlic, rosemary, thyme, olive oil, salt, pepper, and lemon juice to create a marinade.

Rub the marinade all over the leg of lamb, ensuring it is well coated. Let it marinate for at least 1 hour at room temperature or overnight in the refrigerator.

Place the marinated leg of lamb in a roasting pan and insert a meat thermometer into the thickest part of the meat.

Roast in the preheated oven for about 1.5 to 2 hours, or until the internal temperature reaches 135°F (57°C) for medium-rare.

Remove the lamb from the oven and let it rest for 15-20 minutes before carving.

Slice and serve with your choice of sides.