This salad goes well with baked salmon, sauteed shrimp, or grilled chicken.
Preheat oven to 450 degrees. On a large rimmed baking sheet, toss sweet potatoes with 1 tablespoon olive oil; season with salt and pepper. Roast until tender and browned, 15 to 20 minutes. Let cool to room temperature.
In a large bowl, whisk together 2 tablespoons oil, grated orange zest, orange juice, and white-wine vinegar; season with salt and pepper. Add sweet potatoes, arugula, and feta. Toss to combine and serve immediately.