Place foil over the roasting pan, making sure it does not touch the lamb, and roast in a 325 degrees F oven for about 1 hour. Remove the foil and return the roasting pan to the oven for another 15 to 20 minutes or until the lamb temperature registers 125 degrees F.
Let rest. Remove the pan from the oven and let the leg of lamb rest for about 15 to 20 minutes before serving (the lamb will continue to cook and its internal temperature will continue to rise to around 130 degrees F).
Serve. Place the roast lamb and potatoes in a large serving platter over a bed of rice, you like. Garnish with parsley. Or, you may carve the lamb first, then arrange the sliced lamb with the potatoes over the rice.