Preheat oven to 375°F.
Rinse and peel squash. Cut off ends and discard. Cut squash at the neck, creating a narrow end and a round end. Cut round end in half and scoop out seeds with a spoon. Cut both ends into ¾-inch, even-sized cubes.
Coarsely chop walnuts. Set aside.
In a large bowl, add squash. Toss with oil, sage, salt and ground black pepper.
Spread squash evenly on a baking sheet. Roast, stirring once, until tender, about 35 minutes.
In a small skillet over medium heat, melt butter or heat oil. Add walnuts and cook until fragrant, about 2 minutes. Remove from heat. Stir in cranberries and maple syrup.
Gently toss cooked squash with cranberry mixture.