Preheat the oven to 450°F. Brush the baking dish with a little olive oil.
In a large bowl, combine the potatoes, Gruyère cheese, shallots, rosemary, and olive oil, and season with salt and pepper.
Arrange half of the potatoes inside the dish in concentric circles, overlapping the slices slightly. Sprinkle with about half of the Parmesan cheese. Repeat the process once more with the remaining potatoes and Parmesan.
Roast for 30 minutes, or until the top is golden and the potatoes are tender, and serve.