You might want to coop them up for a few days and nights, if your coop is big enough, 'force' them to get familiar with the new roost and feel most comfortable there and establish some new habits.... and not allow the tree roosting to become a habit.
Ditto Dat!!^^^
If you keep them from flapping right off the get go, things stay much calmer.
Don't begin to release your hold until their feet are well settled onto the roost.
They might not stay, but you can't really force them to, just keep trying each night to get few up there.
Is there plenty of room lengthwise on the roost....like at least 8-12" per bird?
Are the roosts wide and flat(2x4, wide side up, works great)?
Is the roost easy to access, both getting up(head room) and getting down(fly/jump off with crashing into a wall)?
Pics of your coop and roost might...