Preheat oven to 500ºF.
Cut each onion into 6 wedges, leaving root end attached. Peel outer skin off the onion wedges and arrange them on a baking sheet. Dress with EVOO to coat and season with rosemary, salt and coarsely ground pepper. Roast 20-25 minutes, until caramelized at edges and tender. Serve warm or room temp as-is or with balsamic drizzle.