Line 2 heavy large baking sheets with silicone baking sheets or parchment paper. In a food processor, chop the Parmesan, Gruyere and rosemary together until coarsely chopped. Set the cheese mixture aside. Separate the dough strips. Using a pizza cutter or a large sharp knife, cut each dough strip in half lengthwise to form thin strips. Working with dough strip at a time, coat each strip with the cheese mixture, pressing very gently. Twist each cheese covered dough strip and place onto prepared baking sheets. Sprinkle with the salt, if you wish.