My artistic adviser, Mrs Chas, advised that the roof really needed terracotta ridge tiles to finish it off. She was absolutely right. She always is. I wondered how to make them but could think of nothing other than bits of styrene strip glued on to the paper tiles with Mek-Pak and topped with styrene rod. Perhaps there is an easier or better method. Something more ornamental would be beyond my ability to make but I suppose the serrated edge of a greetings card might work.
I bought this gadget some time ago for cutting lots of small lengths of styrene strip. It's wonderful.