Preheat oven to 400°F.
Combine pears, squash, tomatoes, leek, garlic, oil, 1/4 teaspoon salt and pepper in a large bowl; toss to coat. Spread evenly on a large rimmed baking sheet. 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 stir in the remaining 1/4 teaspoon salt.
Cook the soup over medium-low heat, stirring, until hot, about 10 minutes. Divide among 6 bowls and garnish with cheese and chives (or scallion greens).