After carving your pumpkin place the mass of pumpkin seeds in a colander and run under water to rinse and separate the seeds from everything else.
Measure out the amount of pumpkin seeds. Add 2 cups of water and 1 tablespoon of salt to the pan for every half cup of pumpkin seeds. Add more salt if you would like your seeds to be saltier. Bring the salted water and pumpkin seeds to a boil. Let simmer for 10 minutes. Remove from heat and drain.
Preheat the oven to 400°F. Coat the bottom of a roasting pan or thick baking sheet with olive oil, about a teaspoon or so. Spread the seeds out over the roasting pan in a single layer, and toss them a bit to coat them with the oil on the pan. Sprinkle with garlic powder and cayenne pepper (optional).
Bake on the top rack until the seeds begin to brown, 5-20 minutes, depending on the size of the seeds. When lightly browned, remove the pan from the oven and let cool on a rack.