If roasting vegetables, preheat oven to 400°. Cut squash lengthwise and scoop out seeds. Spray a baking sheet with cooking spray and place squash on it, cut side down. Place sweet potato on baking sheet or on oven rack. Roast until soft, about 45 minutes for squash halves and 20 to 25 minutes for cubed squash.

Meanwhile, heat oil over medium heat in a large saucepan. Add onions and cook until clear. Add ginger, cumin, salt, and chicken broth. Stir until ingredients are well combined. When squash is done and cool enough to handle, scoop it from its skin and add to saucepan. Do the same for the sweet potato. Stir thoroughly. Transfer mixture in batches to a food processor or blender and puree each batch until smooth, about 3 to 5 minutes. Return pureed mixture to saucepan. Add cream and heat gently until warm. Serve immediately.