Nice, videos, thanks. Ok, Lynx and Red Bull helicopters can do a barrel roll (I have seen the one with Lynx about a year ago). Apache did a loop only, which I was not arguing about (thus the third video is not applicable), as well as most common attack helicopters I know.
There is just too little momentum for a helicopter to do a barrel roll. You need to have enough speed to do that, so very agile lightweight helicopters should be fine, i.e. littlebird etc, but not the heavier ones.