Preheat oven to 400 degrees. Salt and pepper the lamb and set in the roasting dish. In a small bowl mix butter, garlic, thyme, oregano, rosemary, salt and pepper. Rub all of the butter on the outside of your lamb.
In a roasting dish add the potatoes and toss with olive oil and salt and pepper. Lay the lamb roast on top of the potatoes.
Roast in the oven until the internal temperature reaches 145 degrees. About 1 1/2-2 hours. Remove the twine and serve.