I read through this thread with interest, trying to understand the "roll" idea (which I think I get: you rotate the firearm along the axis of the barrel) and what would be so unique about it.
It's something I've always done with a semi-auto as it makes it just that much easier to rack the slide. Why would anyone NOT do it??? Then, it dawned on me...
I'm left-handed. Rolling the firearm of course makes perfect sense as it puts the slide that much closer to my support (right) hand, and has the benefit of pointing the ejection port "down" (rolled 90 degrees from the normal vertical pistol hold) just by the nature of left-handed mechanics. Thinking about it from a right-handed perspective I can see how it could be seen as awkward to roll the firearm to an ejection port down orientation, reaching over the top and trying to rack the slide.