Preheat the roaster oven to 325°F
Remove the ham from packaging and discard any glaze packet if not using
Place the roasting rack in the roaster pan
Add a small amount of water to the bottom of the pan if desired
Place the ham on the rack, cut side down if applicable
Cover the roaster with the lid
Cook the ham until heated through
Estimate about 15 to 20 minutes per pound for a fully cooked ham
Check the internal temperature with a meat thermometer
Remove the ham when it reaches 140°F for a fully cooked ham
Remove the ham when it reaches 145°F if cooking a raw ham
Brush on glaze during the last 20 to 30 minutes if using
Return the lid and continue cooking until the glaze sets
Remove the ham from the roaster
Let the ham rest for 10 to 15 minutes before slicing
Slice and serve