If you import a Skeletal Mesh from, for example but not exclusively limited to Unreal Engine, and characterize it, the Skeleton will appear fine Root is at the top and everything underneath it.
When you export it with a Root Motion Animation and try to apply that to the original character in a project in Unreal, errors will fire off in Unreal Engine in relation to bones transform. After Inspecting it, you will find that the animation has no root motion anymore.

If you Export the character itself it will have another Root Bone named RL_BoneRoot with the original Root Bone named Root underneath it as a child.
This also applies to IK Bones, if the character already has them upon importing they will be renamed to for example ik_foot_root_0, ik_foot_r_0, etc. New IK Bones will be added and those will be constrained on Export.

Steps:
Import Character
Characterize
Export with Animation
Import into Unreal

Actual Result: Root Motion gets stripped due to some Transform error.

Expected Result: The Heirarchy is preserved on the characters and the root motion is applied properly.