Turn your grill to smoke mode, let the fire catch and then set to 350 degrees F (177 degrees C) to preheat.
After removing the seeds from the pumpkin, rinse the seeds under cold water to rid of any leftover pulp.
Toss pumpkin seeds in a bowl with melted butter to coat them, then toss with cinnamon and sugar. Spread the seeds in a single layer on a baking sheet. Roast for about 25 minutes or until lightly golden.