That is a generalization and absolutely not true for all -I would guess many -hotels. Prepaid non refundable reservations are usually by terms of booking not changeable for any reason. Many hotels do not want their rooms resold and if you think about it there is no real incentive for them to work with this company. After all - if the booking is prepaid with no refunds they get their money whether the room is occupied or not. The hotel "is getting their money" without any help from Roomer.

This is my industry and I am not and was not interested in working with them. So just be aware that they cannot resell your rooms unless the hotel has an agreement with them permitting this. Don't pre purchase non refundable reservations with the expectation that you are guaranteed the ability to resell them.