How to apply a custom rig to imported motion?

First, an advanced foot roll IK rig was created using this method.

Next, turn on "FK To IK Conversion" and import the AnimationClip.

The imported motion works fine.

However, since IK_Foot_R exists as a child of the Foot rig

The created foot roll IK rig remains in the initial position.

I want the foot roll IK rig to exist at the foot position of the imported motion.

I would like to import the animation clips so that I can use the foot roll IK rig, any ideas?