* You can ask the butcher at any grocery store to butterfly this for you, just tell them you're making a roulade. Otherwise, you can easily do this at home. Simply slice the roulade, lengthwise, making sure not to cut it all the way through - you want to slice it so it opens like a book. Check out this video
here.
** Perilla/Sesame leaves have a grassy, somewhat bitter taste that is served with Korean BBQ. They can be found at any Korean grocery store and most general Asian grocery stores.