Serve the hens with roasted sweet potatoes: Prick four sweet potatoes all over with a fork and rub the skins with extra-virgin olive oil. Place a large ovenproof skillet, preferably cast iron, on the floor of the oven while it is preheating. Roast the potatoes in the skillet, turning them a few times, for 45 to 55 minutes. (This gives the spuds a blistered, crispy skin.) Halve the potatoes lengthwise just before serving them.