Rinse the pumpkin seeds in a colander under cold water to remove any pulp or strings from the pumpkin. Pat them thoroughly dry with a clean kitchen towel or paper towels. For the crunchiest seeds, let them air dry for a few hours or overnight on a baking sheet.
Preheat your oven to 300°F (150°C). In a medium bowl, toss the dry pumpkin seeds with olive oil or melted butter until every seed is evenly coated. Sprinkle the dry ranch seasoning, garlic powder, onion powder, and salt over the seeds and toss again to distribute the flavors evenly.
Spread the seasoned seeds in a single layer on a large rimmed baking sheet lined with parchment paper. Place in the oven and roast for about 45 minutes. Stir the seeds every 15 minutes to ensure they brown evenly and to prevent the spices from burning on the bottom.
Remove the tray from the oven once the seeds are golden brown and fragrant. Let them cool completely on the baking sheet; they will continue to crisp up as they reach room temperature. Resist the urge to eat them while they are hot for the best texture!