Preheat your oven to 400°F. Line a large baking sheet with parchment paper or foil to make cleanup easy. A light coat of olive oil on the sheet also helps with crisp edges.
In a large bowl, combine the butternut squash, sweet potatoes, brussels sprouts, and red onion. Drizzle with olive oil and sprinkle with salt, pepper, garlic powder, and cinnamon. Toss everything together until evenly coated.
Spread the seasoned vegetables in a single layer on the prepared baking sheet. Try not to overcrowd—this helps them get crispy instead of steaming. Roast for 25 to 30 minutes, stirring halfway through, until tender and golden brown.
While the vegetables are roasting, heat a small saucepan over medium heat. Add the walnuts and toast for 2 minutes, stirring constantly. Drizzle in the maple syrup and a pinch of sea salt. Cook for another 2 to 3 minutes, stirring to coat the walnuts evenly. Remove from heat and let cool on parchment paper.
Once the veggies are fully roasted, remove the tray from the oven. Toss in the dried cranberries and maple-glazed walnuts. Gently mix everything together on the sheet so the flavors mingle while still warm.
Transfer to a serving bowl or platter. Garnish with a sprinkle of fresh herbs if you like—thyme or parsley adds a lovely touch. Serve warm and enjoy all the cozy fall flavors in one bite.