Nothing is simpler than roasting a turkey. You put the bird in the oven. You take it out of the oven. Before you roast, you probably need to thaw. Change water every 30 minutes to keep it cool enough to prevent bacterial growth.
Time is the only variable.
Use a per-pound chart to help you plan the timing of your other dinner dishes, but for perfectly cooked meat, you'll need a meat thermometer. If you use a traditional thermometer that goes into the oven with the bird, place it in the thickest part of the thigh, not touching the bone. If you use an instant-read thermometer, remove the meat from the oven before you test the temperature, either in the thigh or in the thickest part of the breast. 2 to 3 days 6 to 9 hours 16 to 20 lbs. 3 to 4 days 9 to 11 hours 20 to 24 lbs.