Preheat oven to 250°F. Cut off top 3 to 4 inches of pumpkin then scoop out seeds onto a clean work surface. Discard stringy fiber from seeds along with any seeds that are split or cracked then transfer to a strainer and rinse well. (You should have about 2 cups of seeds.)
In a medium pot, bring water to a boil. Add seeds, reduce heat and boil gently for 10 minutes. Drain well and pat dry.
Transfer seeds to a medium bowl, toss with oil and spread out in a single layer on a large baking sheet. Roast seeds, stirring every 10 minutes or so, until just crisp and golden brown, about 1 hour total. (They will become crispier as they cool.) Set aside to let cool completely then shell or eat whole.
For spicy pumpkin seeds, mix 1/2 teaspoon each garlic salt, cumin, coriander and cardamom with seeds and oil before roasting. For sweet pumpkin seeds, mix 1 teaspoon each ground cinnamon, cloves and ginger and 1 1/2 tablespoons dark brown sugar with seeds and oil before roasting.
Recipe Credit: Whole Foods Market website.