I think you are right. Rolls or buns. Sometimes in a sandwich type of food. I am Ito Canadese and spoke Italian at home but a dilect. We would spend our summers in Italy. They didnt have sliced bread the way we do in North America. So the put sandwich meat etc. In a bun.
It's not wrong - just that Duo can't understand the contracted English of "the woman's" meaning "the woman is". It thinks that you are saying "of the woman". I find that it's best not to try to confuse Duo with too much "conversational" English - better to play it at its own game and keep written answers formal.