We always did this when I was a kid, and now, whenever I smell pumpkin seeds roasting I am reminded of my childhood Halloweens, sitting on the kitchen floor designing our oh so creative carving plans (so dad can cut the masterpiece) while up to our elbows in slimy orange pumpkin guts from scraping out and the sorting the seeds from the goopy stuff. (That is a great job for kids by the way)
The hardest part of roasting is keeping an eye on the seeds and stirring them often so they don't burn. Check on them every 5-10 minutes.
Scrape out the seeds and fibers from the pumpkin and place in a bowl (from a hole in the top if it's for carving)
Place the seeds in a bowl and drizzle with 1-2 tsp oil. Add your favorite seasonings ( I usually use garlic and season salt but you could add chili powder, cayenne, Cajun spice, etc) and toss to coat the seeds.
Spread the seeds onto a foil lined baking sheet.
Bake at 300 F for 20-30 minutes (or until light brown) checking and stirring every 5-10 minutes.
How to Roast a Pumpkin