Container planted trees

I have a client that has a nice roof top set up with a few containers with trees and flowers. I maintain his ground level garden and property. A few of the trees are not doing to well. When does the tree roots get to big for the container? Is there added maintenance to a tree planted in a container opposed to the ground?

I have not done much with containers outside of annual color changes and less with trees.

Any pointers for these?

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Container planted trees