Assuming we don't prefer to keep the lens vertically when not attached to a camera.
I'm broadly referring to adding some sort of an attachment to keep it from rolling and falling of a table. Or any other ideas that keep lenses safe.
Have a horizontal box or tray for it.
Get or make a square lenscap. (Front or rear)
Large lens has a tripod mount: keep a plate attached, or insert a spare hotshoe-tripod adaptor or something.
Two rubber bands and popsicle sticks.
Roll it up in flubber.
Put non-rolling objects (including short lenses kept vertically) on either side.
Put them on a towel/soft mat/felt
If you are changing lenses, don't you have a case?
Sugru. It's a moldable silicon (I think) type of putty that becomes completely inert once it dries.
You can do tons of stuff with it, including making unobtrusive but functional no-roll stops.
I have used this for all kinds of repairs/mods and it sounds like just the thing you're looking for.