toddcshoe, to answer your question:
No, the grip ring does not contact plane of surface when the flashlight is lying on its side.

Thank you for the Surefire combat rings link. With my calipers, measurement of body tube (where knurling is at ) is 25.04mm. So the Surefire combat ring with single protrusion and othter one with plastic ring finger hole both look like they will stop a roll. (And since reported inner width of combat ring is one inch should work though may need to add grip tape to portion of flashlight tube it will attach to). If I do not get other replies for anti-roll mods ideas, I may end up buying those combat rings.

The reason I mentioned in OP Fenix TK47 is because reviews of it also mention negative is no anti-roll feature. . It appears to me no anti-roll is at least common with such shaped flashlight: what I would call toilet-plunger shaped.