Preheat oven to 120⁰c. Cut off the top of the pumpkin (about the top 3 to 4 inches) and scoop out the seeds. Throw away stringy fiber from the seeds along with seeds that have split of cracked. Place all the rest of the seeds into a strainer and rinse well. This should leave you with about 2 cups of seeds.
Bring the water to a boil in a medium pot. Then add the seeds and reduce the heat. Boil gently for about 10 minutes. Drain the seeds and transfer on a paper towel to pat dry.
Put the seeds in a medium bowl and toss them with oil. Spread them out in a single layer on a large baking sheet. Place the seeds in the oven for roasting and stir them every 10 minutes of so for about an hour, or until they are crisp and golden. (They will become crispier once you take them out and leave them to cool). Set the seeds aside to cool completely. You can eat them whole or shell them.
If you want to try spicy pumpkin seeds, mix ½ a teaspoon of garlic salt, cumin, coriander and cardamom with the seeds and oil before roasting. For sweet pumpkin seeds mix 1 teaspoon of ground cinnamon, cloves and ginger and 1½ tablespoons of dark brown sugar with seeds and oil before roasting.