When I built my first coop & run I made a "temporary" roost in the run by fastening a 2X4 between two saw horses. Temporary is still there after a year & a half and the girls love it. I plan on building a couple of permanent perches in the new run for the 2nd coop. Try something cheap & easy and see if they like it.
I did that once before. We had cut down a huge mulberry tree and I took a piece
of it with limbs of varying heights and buried out in their run like a post. They seeemed
to enjoy but, started perching on it at night instead of heading to the coop.