Heat oven to 200C/180C fan/gas 6. Toss the veg with 2 tbsp curry paste and the coriander stalks, then season. Divide between 2 trays lined with baking parchment and roast for 20 mins. Turn the veg, then swap the trays around in the oven and cook for a further 15 mins.
Heat the rest of the curry paste with a splash of water, add the onion and cook until soft. Add the roasted veg and stock, and simmer until the veg is tender. Add the coriander leaves and blitz with a hand blender. Return to the heat, add the coconut milk and warm through.
Brush the naan breads with garlic oil, sprinkle with seeds and bake for 3 mins. Serve alongside the soup.