Pre-heat oven to 200C/390F. Heat the oil in an ovenproof dish and roast the carrots for 25 minutes or so until lightly golden and tender. Set aside.
Melt the margarine in a large pan, add the onion, garlic, ginger, lemongrass, chili, curry powder and coriander and cook over a low heat for 5 minutes to allow the spices to release their fragrances. Stir in the roasted carrots, coconut milk and stock and bring to the boil. Reduce the heat to low and simmer gently for 8-10 minutes.
Remove from the heat and season with salt and pepper to taste. Add the lime juice and coriander and stir well. Serve hot.