Mark, my garden was basicaly a court yard when I raced in East London, it ws between 2 terraces of houses and the first I saw of a bird was when it fell from the sky but they still didn't go on the roof!
If you've allowed them to from youngbirds they always will, dog behind the loft or not!
Don't allow them to get into bad habbits in the first place as they are hard to break.