The rock legends played the second of two Sin City shows at the T-Mobile Arena on Saturday, and they surprised fans by introducing Bach to the stage to share vocals on "My Michelle", reported Rolling Stone magazine.
Bach is a familiar face to G N' R fans as he has been a frequent guest at the group's live gigs since 2006, joining Rose to belt out the "Appetite for Destruction" track.
However, Saturday's show marked Bach's first time in the limelight with the classic G N' R line-up, featuring guitarist Slash and bassist Duff McKagan, and he revelled in the opportunity to rock out with the iconic musicians.
Rose was forced to sit for much of the Vegas shows after breaking his foot during the band's 'secret' set in Los Angeles on April 1, the first time the singer had hit the stage with Slash and McKagan since 1993.
He performed at Friday and Saturday's concerts sitting on a throne borrowed from Foo Fighters star Dave Grohl, who had to play shows while seated last year after breaking his leg.