On a large baking sheet, toss the cubed pumpkin with olive oil, salt, and pepper. Spread the pumpkin in a single layer and roast for 25-30 minutes, or until tender and caramelized, turning halfway through.
In a large pot over medium heat, add a splash of olive oil and sauté the chopped onion until translucent, about 5 minutes.
Add the minced garlic, ginger, cinnamon, and nutmeg to the pot, cooking for another 2 minutes until fragrant.
Once the pumpkin is roasted, add it to the pot along with the vegetable broth. Bring to a boil, then reduce heat and let simmer for 15 minutes.
Remove the pot from heat and use an immersion blender to puree the soup until smooth. Alternatively, carefully transfer the soup to a countertop blender in batches, blending until creamy.
Stir in the coconut milk and heat gently until warm. Adjust seasoning with salt and pepper to taste.
Serve your creamy roasted pumpkin soup hot, garnished with fresh sage leaves.
Notes
For a spicier version, add a pinch of cayenne pepper.