I have found when young birds are learning to fly and are well fed and then liberated, they seem happy enough to settle on the loft and soak in the sun. This of course can lead to bad habits and ruining birds that would have otherwise been good kit birds and performers.  

The solution I have found that works best for me is to keep the birds a little on the hungry side. When they are released for training under this condition, I have found them to be more excited and apt to fly around with little if any coaxing.  

My observation is that hunger makes them more agitated and therefore more readily to take to the air. So if you want to get those youngsters off the roof and developing good habits, keep them hungry by feeding a little less. 

By the same token, if you lower the feed too much, you will have the opposite effect and they will only want to come into the loft to eat. You will need to find the right balance so experiment a little.

Tony Chavarria