Parmesan is much easier to find than Pecorino Romano, but it’s not a solid replacement. Pecorino Romano contains so much flavor and the cheese melts so perfectly into a sauce. Plus, if you want true, authentic tasting Bucatini Cacio e Pepe, you’re going to want to stick with the most authentic ingredients possible! If you can’t find Pecorino Romano cheese at a specialty grocery store near you, parmigiano reggiano will work in a pinch.