1. Preheat oven to 425 degrees Fahrenheit (220 degrees Celsius). If using a fresh onion, begin sautéing it with a little oil in a medium frying pan now.
2. Place sweet potatoes onto baking sheet and drizzle with oil, tossing to coat. Roast for 25 minutes and remove from oven.
3. In the meantime, combine crumbs and spices in a large frying pan and toast over medium heat until beginning to brown. Add sweet potatoes and onions and toss, continuing to sauté until sweet potatoes are soft and fully coated.