Preheat your oven to 400°F (200°C).
In a large bowl, toss the cubed sweet potatoes with 1 tablespoon of olive oil, salt, and pepper. Spread them out on a baking sheet.
Roast the sweet potatoes in the oven for 25-30 minutes, or until they are tender and golden brown, flipping halfway through.
In a small bowl, whisk together the remaining olive oil, balsamic vinegar, honey, salt, and pepper to create the dressing.
In a large salad bowl, combine the roasted sweet potatoes, baby spinach, crumbled feta cheese, and sliced red onion.
Drizzle the dressing over the salad and toss gently to combine. Serve immediately.