Scoop out the seeds: Pull the seeds from the pumpkin pulp with your hands, picking out the stringy bits as you go. Set them in a colander.
Rinse under cold water: Run the seeds under cold water, rubbing with your fingers to remove any clinging pulp. Rinse until the water runs clear.
Dry the seeds thoroughly: Spread the seeds on a kitchen towel or paper towels and let them sit for at least 20 minutes. Dry seeds roast crisp, wet seeds steam instead.
Preheat the oven: Set your oven to 325°F and line a baking sheet with parchment paper. A lower temperature keeps the seeds from scorching before the inside dries out.
Toss with oil and salt: In a bowl, toss the dried seeds with olive oil and salt until every seed is coated. This gives any extra spices something to stick to.
Add your flavor mix: Stir in garlic powder, chili powder and lime zest, smoked paprika, or cinnamon sugar depending on the flavor you want. Skip this step for a plain salted batch.
Spread in a single layer: Pour the seeds onto the prepared baking sheet and spread them out so they aren't touching. Crowded seeds steam instead of roasting evenly.
Bake and stir once: Roast for 20 to 25 minutes, stirring at the 12-minute mark so all sides color evenly. Watch for the shells turning golden brown.
Add cheese near the end: If making the garlic parmesan version, sprinkle grated Parmesan over the seeds for the final 5 minutes of baking. This lets it crisp without burning.
Cool before eating: Let the seeds cool on the baking sheet for 10 minutes; they crisp up further as they sit. Toss warm seeds in cinnamon sugar right away if using that flavor.