The paradox of trying to respond properly to technique without the ability to truly feel nage's movement was a curiosity that I only began to understand when I gave up trying to figure it out.
Ukemi, as much as anything, teaches the effect of technique and being willing and capable of moving is a pre-requisite to ukemi. Rolling is one of the best teachers of movement. The mat instructs us immediately on our success and successful rolling requires relaxed, extended, centered movement.
The link below is a video by Donovan Waite, Sensei, who thoroughly explains the concept of "meeting the mat".
