This is a very simple, but delicious side dish that goes with just about any meal. Instead of balsamic vinegar, you can drizzle with a bit of honey and sprinkle with cinnamon.
Preheat oven to 425 degrees F.
Mix sweet potatoes, sweet onion, and garlic in a bowl. Drizzle olive oil over the mixture and season with salt and pepper. Toss to coat, then pour into a shallow roasting pan.
Roast sweet potato mixture in preheated oven, turning frequently, until the vegetables are soft and golden brown, 30 to 35 minutes. Drizzle balsamic vinegar over the vegetables.