
Their background isn't very clear, but apparently they are supposed to look like Martin Luther's symbol of the rose, which had five points. Another theory is that it represents a bishop's miter (yeah, I had to look it up, it's one of those pointy hats Catholic bishops wear).
But anyway, I love Reformationsbrötchen and on Reformations Day tomorrow I'm going to bake some. You can read more about them here (in German--translate on Google if you can't understand).