Heat the oil in a large skillet over medium high heat. Add the sausages and cook until well browned on all sides, about 10 minutes. Remove the sausages from the pan and set aside. Pour off all but 1 tablespoon of oil. Add the onions and cook, stirring, until golden, about 5 minutes. Stir in the tomato paste and cook for 1 minute more. Add the peppers, garlic, and season with salt and pepper to taste. Cook until the peppers are wilted, about 5 minutes. Return the sausages to the pan, cover, and cook over medium heat, stirring frequently, until the sausages are cooked through, about 12 minutes more. Stir in the vinegar. Divide the sausage and peppers evenly amongst the crusty rolls and serve.