A much slower but more effective way to model roof tiles and ridge tiles.
Step by step guide to Tiling Roofs.
I've tiled most roofs on Snitzl Town using this method, and there's no doubt in my mind that the overall look is well worth the time and effort. Its worth modeling the odd building with larger tiles, and that might be a good starting point. Try not to get to much liquid poly under the tile, because really thin styrene tends to distort. Use a small artists brush, not the one in the pot.