Adjust oven rack to lower-middle and preheat to 400°F (200°C). In a 10-inch cast iron skillet, toss sliced mushrooms with smoked paprika, salt, pepper, and olive oil to evenly coat.
Roast mushrooms, using tongs or a wooden spoon to toss occasionally, until very well browned and edges are crispy, 35 to 40 minutes. Serve hot or at room temperature.
