Toss sweet potato cubes with 1 tbsp olive oil, salt, and pepper. Spread on a baking sheet and roast for 20–25 minutes until tender and slightly caramelized, turning halfway through.
In a large bowl, combine roasted sweet potatoes, red bell pepper, red onion, parsley, and feta (if using). Pour the dressing over and toss gently.
Sprinkle with seeds if desired. Serve warm or at room temperature.