Preheat oven to 425 degrees. Pulse pumpkin seeds in a food processor until finely ground. Toss parsnips with oil and ground seeds in a large bowl until evenly coated; season with 1 teaspoon salt and pepper to taste. Arrange in a single layer on 2 rimmed baking sheets. Bake, rotating sheets and tossing parsnips halfway through, until golden brown and crisp, 20 to 25 minutes. Serve immediately.