Preheat oven to 425°. Place tomatoes, onion, carrots, and garlic on an unlined baking sheet (I leave the garlic in a small pile). It will fit pretty snuggly. Drizzle everything with olive oil, salt, and pepper.
3 lbs roma tomatoes*, 1 medium sweet or yellow onion, 3 tablespoon garlic, minced, 3 large carrots, ¼ cup olive oil, ¾ teaspoon kosher salt, ¼ teaspoon black pepper, ground