Preheat your oven to 425°F (220°C).

In a large bowl, combine the chopped carrots, zucchini, red bell pepper, and onion. Drizzle with olive oil, then sprinkle with salt and black pepper. Toss to coat the vegetables evenly.

Spread the vegetables in a single layer on a baking sheet. Roast in the preheated oven for 25-30 minutes, or until the vegetables are tender and slightly caramelized.

Once roasted, transfer the vegetables to a large pot. Add the vegetable broth, heavy cream, garlic powder, and dried thyme. Bring to a simmer over medium heat.

Use an immersion blender to puree the soup until smooth. If you don’t have an immersion blender, carefully transfer the soup in batches to a regular blender.

Stir in the lemon juice and adjust seasoning if necessary. Heat through for an additional 5 minutes.

Serve hot, garnished with fresh herbs if desired.