It’s unfortunate that you can’t see what his left hand is doing whenever he’s rolling the 64ths. He’s not doing anything at all with his right hand, so he’s not doing any stuttering tricks.
My own guess would be that it’s a function of the pads, not any Cubase plugins.
For example, I’ve got the Korg padKontrol, which has a roll and flam function. You just touch the roll control while hitting a pad to do to this. The position of your finger on the roll control determines how fast it goes. It’s also possible his pads have a hold-to-roll function, where all he has to do is hold the pad down, or maybe hold a certain corner of the pad.