Preheat the oven to 400°F. Line a rimmed baking sheet with parchment paper for easy cleanup.
In a large bowl, combine sweet potatoes and red onion. Drizzle with olive oil and season with salt and pepper. Toss to coat, then spread in a single layer on the baking sheet. Roast for 20 minutes, until fork-tender. Set aside to cool slightly.
In a small bowl, whisk together olive oil, apple cider vinegar, Dijon mustard, honey, cumin, and smoked paprika until smooth.
Transfer the roasted potatoes and onion to a large bowl. Drizzle with dressing and gently toss to coat. Add the cranberries, feta, and parsley. Give everything a light stir, then serve warm or room temperature.