Placing a large pigeon cage on the roof is not a wise choice. First of all, it can be very disruptive to your neighbors, especially if there are too many pigeons or if the large cage takes up a lot of space. Secondly, there is also a risk to the structural safety of the building, as the weight of a large cage may exceed the building's load-bearing limits. Finally, the sound of pigeons chirping in the cage may disturb the neighbors and cause nuisance. Therefore, it is recommended to carefully consider and consult with your neighbors when placing a large pigeon cage on your roof.