Idon't ever remember my mother doing that. here is one from a manual.
Electric Roaster Oven
This tabletop appliance serves as an extra oven for cooking a turkey or large roast. Generally, the cooking time and oven temperature setting are the same as for conventional cooking. Always check the roaster oven's use and care manual for the manufacturer's recommended temperature setting and time.
Preheat the oven to at least 325 °F. Place the turkey on the roaster oven rack or other meat rack so the turkey is raised out of the juices that collect in the bottom of the oven liner. Leave the lid on throughout cooking, removing it as little as possible to avoid slowing the cooking process.
Cooking bags can be used in the roaster oven as long as the bag does not touch the sides, bottom, or lid. Follow directions given by the cooking bag manufacturer, and use a food thermometer to be sure the temperature in the innermost part of the thigh and wing and the thickest part of the breast reaches the safe minimum internal temperature of 165 °F.