One thing that I noticed works brilliantly with "unfamiliar" food is literally having the complete thing displayed on your stand/display/whatever. If you've ever been to Camden Market in London, there's loads of food vendors, and they all do this, they have examples of whatever they are making just sitting there, so you don't even need a menu - just point at the thing that you want and they will make it for you. I think it's the same with these - a roll in itself probably won't attract interest, but display it cut in half so everyone can see straight away what you're selling and it becomes a lot more attractive.