A 5-pound roast chicken cooks in 90 minutes in an oven heated to 425 degrees Fahrenheit, according to Food Network. A fully cooked chicken releases clear juices when pierced between a thigh and a leg.
In addition to adequate cooking time, roast chicken requires about 20 minutes of resting time after cooking. During the rest period, the cooked chicken sits on a platter underneath a tented sheet of aluminum foil. Resting results in moist, succulent roast chicken because it gives the juices time to disperse evenly throughout the meat. When a roast chicken is not rested before carving, the juices run out of the meat, leaving it dry.