Preheat the oven to 200°C/fan 180°C/gas mark 6. Place the sausages in a deep, large oven tray and drizzle with the oil. Roast for 15 minutes.
Remove the tray from the oven and add the onion and peppers. Roast for a further 10 minutes, then stir through the baked beans and spinach and top with the tomatoes. Season with black pepper and bake for a further 15 minutes until cooked. Garnish with the parsley and serve with crusty bread.