Preheat the oven to 400°F (200°C). Line a baking sheet with parchment paper.
- Toss the cubed sweet potato and halved Brussels sprouts with olive oil, salt, and pepper. Spread evenly on the baking sheet.
- Roast for 25-30 minutes, flipping halfway through, until tender and golden brown.
- While the vegetables roast, prepare the cranberry vinaigrette by cooking cranberries, honey (or maple syrup), and balsamic vinegar over medium heat, stirring occasionally until the cranberries burst (about 10 minutes). Let cool for a few minutes, then whisk in olive oil and Dijon mustard. Season with salt and pepper.
- In a large bowl, combine the mixed greens, roasted vegetables, toasted nuts, dried cranberries, red onion (if using), and cheese (if using).
- Toss the salad with the cranberry vinaigrette and serve immediately.