Spare parts!
Awesome! Yours looks just as good as theirs - if not better with the walls with the small upper windows in.
I have a large number of medieval buildings myself and I have found that they look nice with the complete roofs, but the fact you cannot access the interiors really is not good at all (especially for children as they end up just taking the end pieces off). I have decided to order a bunch of roofs with the opening on one side and then on the other side with the dormer window openings to put the windows and chimneys on.
I do not want to use an open back for the houses because each of the gable ends on the old houses is unique.