Preheat your oven to 375 degrees with two racks placed in the middle of the oven.
Grease two (preferably rimmed) baking sheets. Place tomatoes, skin side down, on one of them.
Toss the onions and red peppers lightly with olive oil. Place on the other baking sheet, with the red peppers skin side down. Place the unpeeled garlic on the sheet, too.
Bake for 45 minutes.
Heat your vegetable broth on medium-high heat. Peel your garlic and toss it in. Add roasted vegetables and simmer for ten minutes.
Adapted from Heidi Swanson's recipe for roasted tomato and red bell pepper soup in Super Natural Cooking and Sara of Sprouted Kitchen's recipe for roasted tomato soup.
Yields about 12 cups of soup.
Recipe by Cookie and Kate at http://cookieandkate.com/2011/roasted-red-pepper-and-tomato-soup/