You can definitely make this recipe with cooked sausage. I suggest chopping it up into smaller pieces and then adding it to the sauce at the same time as the sun-dried tomatoes, just to heat through.   The flavor of the finished dish will not be the same, though, if made with already cooked sausage as the sausage drippings from cooking it raw, which have loads of flavor, will not be present. Perhaps add an extra drizzle of really great olive oil at the end.