Preheat oven to 400°F (200°C). Toss pumpkin cubes with olive oil, cinnamon, nutmeg, half the curry powder, salt, and pepper. Roast for 25-30 minutes until tender.
In a sauté pan, cook onion, garlic, and ginger in olive oil until softened.
Transfer roasted pumpkin and sautéed mixture to a blender. Add coconut milk and 2 cups of vegetable broth.
Blend until completely smooth. Return to pan.
Add remaining curry powder and maple syrup (if using). Stir in remaining broth and simmer 10 minutes.
Season and adjust consistency with more broth or a splash of coconut milk.