Preheat the oven to 350 degrees F. Spread the Parmesan in a flat, even layer on a silicone baking mat or parchment-lined baking sheet. Bake until the cheese is crisp and golden, about 10 minutes. Let cool, then break into big pieces.
Meanwhile, toast the pine nuts in a medium pan over high heat, tossing occasionally, until golden in spots, 3 to 5 minutes.
Toss romaine, tomatoes, radishes, pine nuts, olive oil, vinegar and some salt and pepper in a large bowl. Top with Parmesan crisps and serve.