This just crossed my wires in my head

Since you do have the original loft kinda empty,,,, Have you considered scanning the stable for some desired colors of the pigeons there, and capturing a few to breed out.

Not sure what kind of access you have there, and the capture would have to be done after dark.
Most of the pigeons there should be of the homing variety. You can possibly run across some runaways with bands. If
I (
just my view) captured them in stable, I would bypass trying to return.

Not many want runaways returned.

(or return them once you got some offsprings

) I don't think you would encounter rollers. They would be first in a feral flock to be eaten by raptors