THANK YOU, THANK YOU to the person that posted the above video. I suffer from a severe case of Murphy's Law and this happened to me! I was so thankful I actually opened the video and watched it, or even checked the forum last week (serendipity at its finest).
As I was putting horses in the field, my older guy went to roll while I was getting the next horse. When I got back, he was flat on his back and not moving. At first I thought the worse but when I called to him, he moved his legs slightly. I can only guess he was thinking of how to get himself out of the mess. I had to dig him out though. The snow was still 2-3 ft in that area and had started to pack to ice. When he went down to roll, he made an ice cocoon while on his back and couldn't move. Poor thing is blind in one eye too and the blind side was up. He was such a good, calm boy. He stayed very still while I dug a 2ft trench around him so he could roll himself upright.
Thanks again to the poster because it saved me some serious anxiety since I immediately knew what was wrong.
Keep an eye on your younger and older horses that may not have the strength to break through the ice topped snow in the fields if they lie down.