First we learned to roll over.  Then we learned to roll over and stay put as in take a nap. Then get on the blanket, take the corner and hold it.  For a long time the 3 things would not come together.  He would let go of the blanket on the rollover.  The blanket was left on the floor and one morning he just walked over to it, grabbed the corner and rolled over in it.

He just needed processing time…