Preheat the oven to 400°F/205°C.Transfer the sliced potatoes, onion and red pepper to your roasting pan.Toss with olive oil, cover and bake for 30 minutes.
Increase the temperature to 450°F/230°C.Remove the foil, add the balsamic marinade and combine. Bake for another 30 minutes. Remove from oven and enjoy!