You're still cutting them with a jig...
I find cutting the shingles to be no less part of building the model than, say, cutting the wall pieces.
It's simple, it's easy, doesn't require special tools and it uses free materials (old cereal boxes and the like). And I don't even find it takes all that much time either.
If you prefer to buy pre-made, that's fine. I was just saying this because it seemed to me there was lack of knowledge about the free and easy choice.