Preheat the oven to 425 F Degrees. Line a sheet pan with parchment paper.
Place the squash and red onion in the baking sheet. Drizzle it with oil and sprinkle it with salt and pepper. Give it a toss.
Roast in the oven for 25-30 minutes or until a knife inserted in a cube of butternut squash comes in and out easily. Set aside to cool.
To Make the vinaigrette: Whisk together oil, balsamic vinegar, dijon mustard, maple syrup, garlic, and salt and pepper.
To assemble: Place baby spinach, quinoa, and roasted vegetables in a large salad bowl. Drizzle it with the salad dressing. Give it a gentle toss.
Top it off with the cranberries, pomegranate arils (if using), and walnuts. Toss and serve.