Preheat your oven to 200°C (400°F). Peel the sweet potatoes and carrots, then chop them into roughly 2 cm pieces. Spread them evenly on a baking sheet, drizzle with 1 tablespoon of olive oil, and toss to coat. Roast for about 20-25 minutes until they are tender and slightly caramelized, filling your kitchen with a sweet, earthy aroma.
While the vegetables roast, heat the remaining 1 tablespoon of olive oil in a large pot over medium heat. Once warm, add the roasted vegetables and sauté gently for 2-3 minutes, allowing their flavors to meld and their edges to begin to soften.
Pour in the vegetable broth, bringing the mixture to a gentle simmer. Cover the pot, and cook for another 10 minutes, giving the flavors time to deepen and the vegetables to become very tender.
Remove the pot from heat. Use an immersion blender directly in the pot or carefully transfer the mixture to a blender in batches. Puree until the soup is completely smooth and velvety, with a bright, rich orange color. Be cautious of hot splashes during blending.
Stir in the miso paste, blending thoroughly to incorporate. Warm the soup gently over low heat for 2 minutes—avoid boiling, as high heat can diminish miso’s flavor. Taste and add salt if needed.
Serve the soup hot in bowls, garnished with a sprinkle of seeds or a dollop of yogurt. Drizzle with a little extra olive oil if desired, and enjoy the comforting, silky texture and layered flavors with every spoonful.