To answer this question, it is first necessary to define the term “roost.”
In its most literal sense, a roost is a support for a bird to perch on. In some cases, the roost consists of a branch or pole which has been cut from a tree and placed on the ground or in another elevated position.
When we refer to “can chickens roost on trees?” it seems that the more appropriate question would be “can chickens perch on trees?”
Perching is different from roosting because it does not involve resting at night and typically only occurs during daylight hours. During perching, birds may remain perched for long periods without moving their wings much.

But to answer your question, YES chickens can roost in trees.
Is it OK to let chickens roost on trees?
Many people argue that chickens should not roost on trees because it makes them more vulnerable to predators.
However, others argue that it actually provides a layer of protection for the chickens.
The roosting position of a chicken is not as important as the type of predator it has to avoid. The critical thing is that there are plenty of other ways to protect chickens from predators and roosting on trees can be one method.
This debate is mainly about what kind of predator the chicken has to defend against and how much effort should be spent defending against those predators. Comparing different methods will show which one is more effective.
Chickens are not meant to be on the trees; they are intended to be in an enclosed environment where they can walk around and enjoy themselves. Being in a tree may seem like a nice alternative at first, but chickens have been known to suffer from various illnesses due to their tree-roosting habits.
Can chickens sleep in trees?
Did you ever wonder if chickens can sleep in trees? It sounds like a silly question, but the answer is not as simple as it seems.
Chickens have been observed sleeping on the ground, on low-hanging branches, and in trees. The University of California at Davis conducted a study to see what breeds of chickens slept in trees.
The study found that the Jersey Giant breed used for meat production sleep almost exclusively on the ground or low-hanging limbs.
On the other hand, Heritage breeds typically used for egg production were observed sleeping up high more often than not.

A study conducted by Purdue University found that chickens slept way up high (in trees) more often than they did on the ground or lower branches. This suggests that yes, chickens can sleep in trees.
How do you stop chickens from sleeping in trees?
Theoretically, if you were to grab the chickens by their feet and swing them around so they were upside down, they would be too dizzy to do anything more than sleep. Wait, what?
However, this is not a very realistic way to stop chickens from sleeping in trees.
A more practical way would be to put up some fake trees around your coop.
The chickens won’t know the difference and will stay away from the trees that are not safe for them.

REFERENCES:
https://forums.horseandhound.co.uk/threads/chickens-roosting-in-trees.766925/

Shannon Stansberry has been engaged in the business of raising chickens for more than 12 years. In 2016, she accomplished the Agriculture & Natural Resources program at Mt. San Antonio College. At present, she tends to more than 80 chickens on her 4-hectare farm. Shannon regularly shares her insights and experience on how to raise healthy and contented chickens on the platform Typesofchickens.com