This is one of several many videos I recall watching recently where a Gunner demonstrates being able to use Stylish Roll or Another S-Roll Arts (my apologies for the fan-translation terminology) repeatedly without ever triggering the third roll that slows down the animation significantly.
The timestamps in that video are the following for quick reference:
I will not be listing every instance of this happening but I have been curious of how players are able to repeatedly use Stylish Roll without stopping to use the third normal attack or use a photon art in-between to pause movement. The only "clue" I have had is that after the second Stylish Roll you could potentially charge up a photon art like Aerial Shooting and then cancel the charge with a Stylish Roll but that does not seem to result in looping Another S-Roll Arts mode several more times afterwards.
I have been wary of asking for help with this simply because it seemed as though this was "common knowledge" especially for the Forever/Eternal titles and for general gameplay and I remember being shamed for not having "smooth enough" Another S-Roll Arts shots when I was originally learning the game with the Gunner even on the Japanese side. Any help with this would be greatly appreciated.