Sorce,
Wow, indeed!
I don't mean to be rude, but folding roots under is just not the way it should be done. It doesn't matter if it's a tropical tree or not.
On collected trees that don't have many feeder roots close to the trunk, what do we do? Do we fold the roots over so the tree will fit in a typical deep nursery can? No, a special box is built so that the roots can lay out flat. Over the next couple years, each time the tree is repotted, the long roots are shortened as new feeder roots are developed.
The whole point of what we try to do with nebari is to build a healthy shallow root system.
Maverick, I have no idea what kind of tree you're wanting to up pot. But here's what you ought to do:
As Cypress187 said, whenever you repot, use that opportunity to improve the root system. Sorce is correct in that "good roots make a healthy tree". I'm not advocating cutting all the roots off, but "up potting" implies that the tree is potbound. In which case there will be a lot of circling roots running around the outside of the rootball.
Those should be removed.
Cut the bottom of the rootball flat with scissors. Make it as smooth and flat as possible.
Tease out 1/4 to 1/2 inch of small roots all along the sides of the rootball. So that the sides look fuzzy. Smooth bottom, fuzzy sides. Then pot it into the new larger pot. Take care to carefully chopstick new soil so that the fuzzy roots are in contact with the new soil. Don't chopstick too much or else you'll damage the fuzzy roots. Back fill and water. Of course, it should be wired in place.
Do not tease the long circling roots out and tuck them under.