Preheat oven to 400 degrees. Place squash, sweet potato and onion in a large mixing bowl. Drizzle with 3 tablespoons olive oil and toss vegetables well. Transfer vegetables to a parchment paper lined baking sheet in a single layer. Bake for 40 minutes, or under tender.
Heat 1 teaspoon oil in a large stockpot. Add red curry paste, ginger and garlic and stir well. Cook until fragrant, about 1 minute. Add vegetable stock, coconut milk, salt and pepper. Bring to a boil, then reduce heat and cook, covered, for 10 minutes.
Place roasted vegetables and stock in a blender and blend until smooth. You will need to do this in several batches, depending on the size of your blender. Return blended soup to stockpot.
Stir in adzuki beans, if desired.