After a few days of trying, last evening our LittleTiger finally managed to roll himself over!
I had kept my camera handy in anticipation and I'd start recording every time he made an attempt.
Unfortunately, I couldn't get it on camera when he finally did roll over. We had some friends over for dinner last night and we were discussing how LittleTiger is really close to rolling over. And ten minutes later, he had done it! Our friend was the first person who noticed it and before I could reach for the camera, he had already turned.
I think he surprised himself at the outcome. He stayed in the tummy-down position for some time, frantically kicking his legs in the air.
He can't roll back to his back yet so eventually we had to go rescue him!