Slice pepper, onion, and tomatoes (in half). Peel garlic. Put in a baking dish with olive oil, salt and pepper. Roast at 450° for 20 minutes. Toss ingredients, then roast for 20 minutes more, or until brown and tender.
While the vegetables are roasting, boil sweet potato until tender. Peel after it has cooled.
Put all the above ingredients plus low sodium vegetable broth, balsamic vinegar, fresh basil, thyme, and more salt and pepper (if needed) in a blender. Process until smooth. Heat on stove for 10 minutes, and serve.