At which point does the Bard use this reaction? Do all his allies roll the saving throw first then the Bard can choose to roll his Counter Performance, or does Bard use Counter Performance before his allies have rolled their saving throws.
I would say after your ally or you rolls the check. The trigger is that you roll a saving throw, not are targeted by an effect, so you would not be able to use the reaction prior to the roll in any case.
That's pretty awesome, so I could roll a saving throw and roll a 12 let's say then say I wanna use my reaction for Counter Performance? Basically I get two rolls, legit.