Place all the veggies on the tray. Drizzle the olive oil and sprinkle the dried basil. Use your hands or a wooden spatula to coat the vegetables.
Roast for 25-30 minutes at 400F.
Transfer the tomatoes and bell peppers to a paper bag and set aside for 10 minutes.
Peel tomatoes, bell peppers and onions. Place in a large pot together with the other veggies. Pour the vegetable stock, season with salt and pepper to taste and blend until smooth.