In a large mixing bowl, combine the diced butternut squash, halved Brussels sprouts, and cranberries.
Drizzle olive oil and maple syrup over the vegetables and cranberries, then sprinkle with salt, pepper, cinnamon, and nutmeg. Toss everything together until evenly coated.
Spread the mixture onto a large baking sheet in a single layer.
Roast in the preheated oven for 25-30 minutes, stirring halfway through, until the butternut squash is tender and starting to caramelize, and the Brussels sprouts are beautifully browned.
If using, sprinkle the chopped pecans over the medley during the last 5 minutes of roasting to toast them slightly.
Remove from the oven and let cool for a few minutes.
Transfer to a serving dish and garnish with fresh parsley before serving.