Preheat oven to 400 °F (204 °C) and place sweet potato and parsnips on baking sheet. Drizzle olive oil generously over the vegetables and season with salt and ground black pepper. Toss to coat. Roast for 25-30 minutes, or until softened.
Once cooked, let cool for 15 minutes then add to the blender along with vegetable stock, ground ginger, and ground turmeric.
Carefully cover the blender with the lid then blend until smooth and creamy.
Add a dollop of mascarpone cheese on top, if desired.