Preheat oven to 400°F. Combine pears, squash, tomatoes, leeks, garlic, oil, salt and pepper in a large bowl; toss to coat. Spread evenly on two large rimmed baking sheets. Roast, stirring occasionally, until the vegetables are tender, 40 to 55 minutes. Let cool slightly.
Place half the vegetables and 2 cups broth in a blender; puree until smooth. Transfer to a large saucepan. Puree the remaining vegetables and 2 cups broth. Add to the pan and cook the soup over medium-low heat, stirring, until hot, about 10 minutes. Adjust seasoning; divide among 6 bowls and garnish with cheese and/or croutons. 6 servings. Soup can be made ahead, and frozen for up to four weeks.