Place the butternut squash, carrots, brussels sprouts, and onion on a baking sheet. Add oil, garlic powder, salt, and pepper. Toss to combine. Make sure vegetables are spread out in a single layer and not overlapping on top of each other.
Roast for 30-35 minutes, or until vegetables are fork-tender.
While the vegetables are roasting, prepare the miso glaze. Whisk together the miso paste, rice vinegar, maple syrup, and grated ginger in a small bowl. Start with 1 tablespoon of maple syrup and taste. The sauce with 1 tbsp is more fermented and tangy - which many prefer! But if you're one who wants it sweeter, increase to 1.5-2 tbsp maple syrup.
2 tablespoons white miso paste, 2 tablespoons rice vinegar, 1-2 tablespoons maple syrup, 1 teaspoon grated ginger
Remove vegetables from the oven and pour the miso glaze over them. Use a fish spatula to carefully toss the vegetables in the sauce.
Return the pan back to the oven on the broiler setting, and broil 1-2 minutes, until vegetables have a slight caramelization and char.
Remove from oven, sprinkle with fresh parsley, and enjoy!