The Lancashire outfit came out of the blocks early with a dominant start leading to a 12-0 lead inside the first twelve minutes of the game thanks to tries from Adam Swift and Johnny Lomax.
However, a strong middle patch of the first-half saw the Robins turn the tide and claw their way back into the game with two tries from Kevin Larroyer and Greg Eden.
At the break the score was tied at 12-apiece, but Saints came out of the sheds after the break and tore apart a ragged Rovers defence.
Four tries in ten minutes ripped the game wide open as Saints showed their superiority as KR were left to contemplate what could have happened.
Saints scored second-half tries through Alex Walmsley, Swift grabbed his second, Tommy Makinson and Jon Wilkin.
These scores put them firmly in control of the game before Josh Hodgson crossed for a late try, which was nothing more than consolation for the visitors.