How to stop chickens from roosting in aframe

[perkolator]

Simply remove that extra 2x4 that's up there; I don't see the function of it aside from another roosting spot

 

[NatJ]

Tonight I put up some mesh netting (that they could see) but they attempted again… and again… and again.

Should I staple cardboard or something more firm up there instead of netting?

Yes, I would try adding something like cardboard that looks more solid. The netting probably looks (to the chickens) like something they can get through if they just keep trying.