Share to: 15 - 30min in a pressure cooker If you are roasting a chicken in a 400 degree oven, you'll probably need to cook it for close to an hour depending on how large the chicken is. â¦ At the one hour mark, check the temperature to see that it's 160 or higher in the breast and the thigh.6 people found this useful.5 - 30min in a pressure cooker If you are roasting a chicken in a 400 degree oven, you'll probably need to cook it for close to an hour depending on how large the chicken is. â¦ At the one hour mark, check the temperature to see that it's 160 or higher in the breast and the thigh. 6 people found this useful.