Preheat your oven to 200°C (400°F). Line a baking sheet with parchment paper for easy cleanup.
Peel and chop the sweet potatoes into roughly 1-inch pieces, and slice the carrots similarly. Peel and roughly chop the onion and leave the garlic cloves whole.
In a large bowl, toss the sweet potatoes, carrots, onion, and garlic with 1 tablespoon of olive oil, a pinch of salt, and pepper. Spread everything out evenly on the prepared baking sheet.
Roast the vegetables in the oven for about 35-40 minutes, until they are deeply golden and caramelized around the edges, shaking the pan halfway through to ensure even roasting.
Once roasted, transfer the vegetables to a large pot. Pour in the vegetable broth and bring to a gentle simmer over medium heat for about 10 minutes, allowing flavors to meld.
Using an immersion blender or a regular blender in batches, puree the soup until smooth and velvety. Be cautious of hot splashes if using a regular blender.
Taste the soup and adjust seasoning with more salt and pepper as needed. Stir in a teaspoon of olive oil for added richness if desired.
Pour the hot soup into bowls, drizzle with a little extra olive oil if you like, and serve immediately for a warm, silky experience.
