Preheat the oven to 180°C.
Peel, then cut the beets into wedges or half (depending on their size).
Cut the onions in half. Lightly crush the garlic cloves (with their skin on).
Cut the pepper into chunks.
Arrange all of them in a baking tray. Tuck the chilli pepper between them, then scatter the oregano on top..
Drizzle with oil and balsamic vinegar, then season with salt & pepper. Toss gently.
Cover the dish with foil, then bake in the oven for 25 minutes. During the baking, toss the veggies once or twice.
Take the foil off and roast for 5 minutes.
When the veggies are tender and golden, remove the dish from the oven.