Preheat oven to 450°F.
Toss squash with oil, nutmeg, salt and pepper in a large bowl. Spread on a baking sheet. Roast until lightly browned, 12 to 15 minutes.
Meanwhile, whisk butter in a small skillet over medium-low heat until melted. Cook until butter begins to brown, 1 to 2 minutes. Remove from heat and whisk in sage, maple syrup and lemon juice.
Arrange roasted squash in a serving dish. Drizzle with butter mixture and sprinkle with pepitas before serving.