Preheat oven to 450F. Coat a rimmed baking sheet or roasting pan with cooking spray.Remove stems from mushrooms. Place mushroom caps, gill-side up, on the prepared pan. Sprinkle with 1/8 tsp salt and 1/8 tsp pepper. Roast until tender, about 20 minutes.
Combine breadcrumbs, Parmesan, parsley, oil, the remaining 1/8 tsp salt and 1/8 tsp pepper in a small bowl. Remove the mushrooms from the oven and top each cap with about 2 tablespoons of the breadcrumb mixture, spreading evenly. Return to the oven and roast until the breadcrumbs are browned, about 5 minutes.