Pre-heat oven to 230°C. Cut potatoes and celery root into 2cm thick matchsticks. In a small bowl, mix together cayenne, paprika, five-spice powder, garlic powder, black pepper and salt.
Spread matchsticks evenly on two sheet trays and toss with oil and spice mixture. Roast until golden brown, about 40 minutes, shaking pan occasionally. Serve immediately.