Heat oven to 300° F. Remove the seeds from the pumpkins. Discard the pulp.
Spread the seeds (no need to rinse them) evenly on an ungreased baking sheet. Bake until dried, about 1 hour.
Toss the seeds, olive oil, celery salt, and cumin in a large skillet. Cook, stirring occasionally, over medium heat, until the seeds are lightly toasted, about 3 minutes.