For crispy skin and even cooking of a roast chicken, you should roast it uncovered for most, if not all, of the cooking time.
The choice between covering and uncovering a roast chicken significantly impacts its texture and cooking process. Roasting a chicken uncovered is the preferred method for achieving that desirable crispy, golden-brown skin. When the chicken is uncovered, the hot, dry air of the oven can freely circulate around its entire surface, efficiently evaporating moisture from the skin. This evaporation is crucial for rendering the fat and crisping up the skin. If you cover the chicken with foil, it traps steam around the bird, essentially steaming it rather than roasting it. This results in soft, pale, and often flabby skin, which is generally undesirable for a roast chicken. While some recipes might suggest covering briefly if the chicken is browning too quickly, for the majority of the cooking time, especially if crispy skin is a priority, leaving it uncovered is key. Proper temperature control and monitoring with a meat thermometer will ensure the chicken cooks through without drying out.
If you notice the chicken skin browning too quickly before the internal temperature is reached, you can loosely tent it with foil for the last 15-20 minutes, but remove the foil for the final few minutes to re-crisp.