Toss sweet potatoes and red onion with 2 tablespoons olive oil, salt, and pepper on a baking sheet.
Spread in a single layer and roast at 400°F until tender, about 25 minutes.
In a small bowl, whisk together apple cider vinegar, Dijon mustard, honey, cumin, garlic powder, and paprika. Gradually mix in the remaining 4 tablespoons of oil.
In a large bowl, combine roasted sweet potatoes, dried cranberries, feta cheese, and cilantro. Pour dressing over the salad and toss to coat evenly.
Adjust seasonings as needed. Serve the salad warm or at room temperature.