Line 2 heavy large baking sheets with silicone baking sheets or parchment paper.
In a food processor, chop the Parmesan, Gruyere, and rosemary together just 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 one 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 salt, if desired.
Bake until breadsticks are golden brown, about 10-15 minutes. Transfer warm breadsticks to a basket and serve.