The most popular drum used in hog roasters is a 55-gallon steel variety. You can purchase these new or find a used one if you are on a budget. If you opt for the latter, make sure you know what the drum originally contained. Make sure it was organic material, and if you are unsure of the drum's previous contents, find a new one. Cut the drum in half vertically. Create a lid for it by mounting hinges, and then drill a hole in the lid where you can place a thermometer. Cut large holes in the bottom half of the drum to act as vents that provide airflow. Also drill a smaller hole in the bottom of the drum to allow grease to drip into a pan.
Make sure the stand on which your hog roaster drum sits is stable and resistant to heat. Remember that homemade roasters usually work best for a specific type of pig that weighs around 20 pounds. If you plan to roast a pig that weighs much more than this, make sure your stand can support the weight.
Lastly, mount a steel rod to the drum and create a bracket so it can spin. A hand crank is impractical since a hog takes several hours to roast. One rotation per minute is a fine speed at which the rod can spin, and any small motor can accomplish this task.