Heat oven to 400 degrees F. Spray a large roasting pan with nonstick cooking spray. Place sausage in the pan and roast for 15 minutes.
Place peppers, onion and potato in a large bowl. Toss with olive oil, Italian seasoning, salt and pepper. Add vegetables to the roasting pan and stir to combine with sausage. Roast for an additional 45 minutes, stirring twice, until vegetables are tender. Remove from oven and stir in vinegar.
To serve, spoon 1 generous cup of sausage and peppers over each toasted bun.