Preheat the oven to 400°F (200°C).
Place the leg of lamb in a roasting pan and rub it with olive oil, minced garlic, rosemary, thyme, salt, and pepper.
Surround the lamb with the potatoes, carrots, and onions.
Drizzle olive oil over the vegetables and season with salt and pepper.
Roast in the oven for about 1.5 hours, or until the internal temperature of the lamb reaches 145°F for medium-rare.
Remove from oven, cover with foil, and let rest for 15 minutes before slicing and serving.