how long to cook lamb by weight
Roast Lamb. Medium - 15 minutes per lb (450g). Well done - 20 minutes per lb (450g). Slow Roasting. The times for the slow roasting method are as follows: Cook in Roasting Oven for about 30 minutes, or until beginning to brown, then transfer to the Simmering Oven for double the remaining cooking time.ell done - 20 minutes per lb (450g). Slow Roasting. The times for the slow roasting method are as follows: Cook in Roasting Oven for about 30 minutes, or until beginning to brown, then transfer to the Simmering Oven for double the remaining cooking time.