A 4.5 lb. chicken is 1.5 lbs. heavier than the 3 lb. chicken used in the recipe that I posted. You should definitely NOT cook it less than the 5 hours and it may take MORE time because you are cooking a bigger bird.

To be safe, you should check the bird with a meat thermometer after 5 hours at 250F in the meatiest part of the thigh. The temp should be up to 180F and if it is not up to that temp, I would put it back in to roast for another 30 minutes, then check the temp again. Poultry should always be throughly cooked and have no pink juices flowing when stuck with a fork or tip of a sharp knife.

Please be careful to check the temp of the bird before you take it out of the oven and pronounce it done.