Clean the pumpkin seeds by placing them in a medium bowl and covering with water. Sift through the seeds with your hands, removing any large or very stringy pieces of squash and separating the seeds. Change the water 1-3 times during cleaning. Note that small bits of pumpkin that are clinging to the seeds are fine and will add flavor.
Drain the seeds in a sieve or colander. (Optional: leave the seeds to dry for several hours or overnight to help shorten roasting time.)
Heat oven to 300°F. Toss the drained seeds with the olive oil and salt. Spread the seeds on a baking sheet and place in the oven. Bake for 45-60 mintues, stirring every 10-15 minutes. When seeds are crunchy and golden brown, remove from the oven to cool. Place cooled seeds in an airtight container and store at room temperature.