I can never resist having a try at a texture when a thread like this crops up. So here goes my try:
I have used one (doubled) tile and instanced it on a subdivided plane.
I used the object location and random outputs to get the random colours and texture mapping.
Here is the file if you are interested (you will not be able to read the nodes from the screenshot):
roof.blend (897.6 KB)
feel free to use, adapt or throw away!