1. Preheat oven to 400°. Spread first 3 ingredients on a baking sheet, and roast on middle oven shelf 20 to 25 minutes or until light brown. Remove from oven, and let cool.
2. Halve tomato quarters crosswise, and pulse in a food processor in 2 batches until coarsely chopped. Transfer to a large nonreactive bowl.
3. Pulse garlic in food processor until finely minced, scraping bowl as needed. Add jalapeño, and pulse until finely chopped. Add tomatillo, and pulse until finely chopped; add mixture to tomato.
4. Chop roasted onion and bell peppers. If bell pepper skins are loose, remove before chopping. Add to tomato mixture. Stir in corn and next 4 ingredients, cover, and chill at least 2 hours.
5. Stir in cilantro, ladle into well-chilled large soup bowls, and garnish, if desired.