Preheat oven to 350 F. Cut pumpkin in half. Remove all the seeds (you can use multiple pumpkins at a time if you wish).
Place raw seeds into a strainer. Wash seeds under cold running water. Let the water drain from the seeds. Place them onto a pan. If you like seeds salted, then sprinkle a little with salt (optional). Roast the seeds for 30 minutes mixing occasionally to prevent the seeds to burn. Then turn the oven off and let the seeds continue roasting for 1 hour or until the seeds are light golden brown and fully roasted inside.
Remove from the oven. Let the seeds cool before consuming.