Polycount doesn't matter when you do it for a render and not for a videogame. I've worked with 10 mil poly scenes before without any issue.

That is kind of true however it will affect performance and rendertime depending on your pc, the roof tile effect can be easily done and faster with bump mapping

I am totally aware of that, however it won't look nearly as good. I was considering using a displacement map, however I wouldn't get the tiles in the places I want them. And my comp can run 10 mil polys without lag, so I have nothing to worry about in the performance department on this. I use layers as well, so I can just hide the parts I'm not working on making performance even less of an issue. And the rendertime on this was 15 seconds, so I wouldn't worry about that too much either.