Preheat oven to 400 degrees. Brush an 8-inch square baking dish with oil; set aside. In a medium bowl, mix squash puree with sage, 1 1/2 teaspoons salt, and 1/4 teaspoon pepper. In another bowl, mix ricotta with 1/2 cup Parmesan, 1 teaspoon salt, and 1/4 teaspoon pepper. Set aside.