Hi,
A root bone is necessary due to this is how Unreal finds the location etc. of the character. If you can post links to what plugins/software you are using, your project/character, and a screenshot of the results you are seeing, I can take a better look at the issue since I have some more information to work with now. I don’t believe notifies would really help you in this case, but I’m not sure of what type of setup you have in mind. It sounds like this issue is occurring due to how the root bone is set up(I would need to see the layout of the skeleton) or due to the retargeting.
-Thank you