Preheat the Oven: Set your oven to 400°F (200°C).

Roast the Vegetables: On a baking sheet, combine zucchini, bell pepper, carrot, and butternut squash. Drizzle with olive oil, sprinkle with Italian seasoning, salt, and pepper, then toss gently. Roast for 25-30 minutes, or until the vegetables are tender and slightly caramelized.

Sauté the Aromatics: In a large pot, heat 1 tablespoon of olive oil over medium heat. Add the onion and sauté until translucent, about 5 minutes. Add the garlic and cook for an additional minute, until fragrant.

Combine Ingredients: Add the roasted vegetables to the pot along with the diced tomatoes and broth. Bring the mixture to a boil, and then reduce to a simmer for 15-20 minutes.

Blend for Texture: Carefully use an immersion blender to puree the soup to your desired consistency.

Taste and Adjust: Check for seasoning and adjust with extra salt or pepper if needed. Let it simmer on low for another 5-10 minutes.

Serve Warm: Ladle the soup into bowls and garnish with fresh basil and a sprinkle of Parmesan cheese, if desired.