Depending on your use case, you may need to set the root bone's location and rotation to zero in Unreal Engine.
Below are some presets to help you position the root bone correctly in Blender:

Note: You will need to re-import the skeletal meshes and animations after every change.

• Head: X=0, Y=0, Z=0
• Tail: X=0, Y=0, Z=1
• Roll: 0°

Standard FBX:

• Rotation: (Pitch=0.0, Yaw=0.0, Roll=90.0)

Custom FBX:

• Rotation: (Pitch=90.0, Yaw=-90.0, Roll=-90.0)

Standard glTF 2.0 (Recommended):

• Rotation: (Pitch=0.0, Yaw=-00.0, Roll=0.0)

• Head: X=0, Y=0, Z=0
• Tail: X=0, Y=1, Z=0
• Roll: 0°

• Head: X=0, Y=0, Z=0
• Tail: X=1, Y=0, Z=0
• Roll: 90°

• Head: X=0, Y=0, Z=0
• Tail: X=0, Y=0, Z=1
• Roll: 0°

By default, Blender's standard FBX I/O API exports the armature object as a root bone.
This addon removes the armature root bone by default. You can modify this behavior in the Addon Preferences:

You can also specify the desired root bone name and scale.
Warning: If the root bone is named "Armature," Unreal Engine will remove it.

• BFU Docs: Unit Scale
• BFU Docs: UE Bone Structure and UE Mannequin
• For community support and discussions, join the Discord: BleuRaven Side Projects