I had this discussion with the counter person at a local bakery this morning, after I ordered a bialy and he said "which kind?" I had always thought that a bialy by definition had onions (and usually poppyseeds) in the middle. But he said no, it just means that the dough has been baked, not boiled, so the other round bagel-looking things in the bakery case were in fact sesame bialys, rye bialys, etc. if that is indeed the case, what makes a bialy any different from a roll? Something about the dough? I tried googling this of course, but didn't get a clear answer as most of the bialy definitions said something like "typically filled with an onion mixture."