On Friday I brought Michael out from the nursery and set him tummy-down on a blanket in the living room. I went back to the nursery for Sophie, returned, and found Michael smiling up at me...on his back. This all transpired literally within thirty seconds. I called Mike to tell him about Michael rolling over and not to feel bad for missing the milestone. So did I!
Michael hasn't rolled again (and Sophie is still mastering holding her head up), but this is video I filmed right after his magic act. You can see it's likely to happen again soon.