Roast vegetables: Place the tomatoes, red pepper, onion and garlic on a rimmed baking sheet. Toss with olive oil, Italian seasoning, salt and pepper. Roast for 20-30 minutes, until softened, fragrant and starting to brown.
Blend: Place the roasted vegetables in a blender and process until smooth (please ALWAYS check manufacturer's instructions for blending hot ingredients; e.g. Vitamix recommends to leave the lid open in the middle and to cover with a tea towel to allow for the steam to escape).
Finish soup: Add the blended vegetables to a large soup pot. Stir in enough broth or evaporated milk to reach your desired consistency. Add heavy cream, if you like, then season with sugar, fresh basil and additional salt/pepper to your taste. Warm through for a few minutes, then remove the basil before serving hot.