Preheat oven to 220°C. Combine cumin, coriander, chilli powder and salt. Combine onion, carrots, chilli, pumpkin, and peppers. Drizzle with oil and add spice mixture, stirring (use hands if preferred) to coat.
Roast veg in large dish (may need two) for 10-15 minutes. Stir and roast another 10-15 minutes until beginning to brown.
Once roasted, combine in large pot with stock, coconut milk, oregano and salt and pepper. Simmer 15 minutes to be sure all veg is tender. Puree until smooth, and serve topped with coriander.