Turn the oven on and set the heat to 450 degrees.
Take the chicken out of its package. Remove the giblets and neck from the chicken cavity. (Yes, this step can be kind of gross). Unless there’s someone at home who wants to use them, throw them away.
Put the carrots and celery in the center of the baking sheet, forming a rack. Put the chicken on the carrot-and-celery rack and rub it with the salt and pepper. Put the lemon quarters in the cavities, which are the openings in the front and back of the chicken. Be sure to wash your hands with soap and water after handling raw chicken!
Once the oven temperature has reached 450 degrees, carefully put the baking sheet in the oven.
After 1 hour and 10 minutes have passed, take the chicken out of the oven to test for doneness. If you are using a meat thermometer, stick the sharp part deep into the inner thigh: the chicken is done when the thermometer reads 165 degrees. If you do not have a meat thermometer, you can tell when the chicken is done with one of these tests: Poke the thigh with a sharp knife and look at the juice that runs out; it should be clear (not pink); Or, wiggle the leg, which should move easily. If it’s not done, put the chicken back in the oven and test it again after 15 minutes.
Let the chicken rest on a cutting board for 10 minutes before carving it.
NOTE: If your chicken is less than 5 pounds, you will need to cook it for less time, averaging about 12 minutes per pound.