Preheat oven to 450 degrees F (230 degrees C). Line 2 baking sheets with parchment paper and spray them with cooking spray.
Drop tablespoonfuls of Parmesan cheese 2 inches apart on the prepared baking sheet. Flatten them out to the size of a potato chip. Sprinkle rosemary and garlic salt on top.
Bake in the preheated oven just until edges start to turn golden brown, 3 to 5 minutes. Cool on the baking sheets for 2 minutes; lift off with a spatula and transfer to a wire rack to cool until firm, about 5 minutes.