Preheat the oven to 375°F (190°C).

In a bowl, mix together rosemary, thyme, parsley, garlic, salt, pepper, and olive oil to form a paste.

Rub the herb mixture all over the leg of lamb, ensuring it is well coated.

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

Roast in the preheated oven for about 90 minutes, 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 minutes before carving.

Slice the lamb against the grain and serve with your choice of sides.