Mathieu Manset and Darren Jones put the Bulls two goals up after 21 minutes before Marc Pugh completed the scoring late on to ensure that Rotherham head into the play-offs off the back of a heavy defeat.
The home side got off to an excellent start and were ahead after four minutes. Pugh got away on the left and delivered a low cross that Manset rifled past Andy Warrington.
Hereford doubled their lead after 20 minutes when a corner was only half cleared to Kenny Lunt and he showed some neat skills before delivering a cross to the far post that Jones headed home.
Leon Constantine struck the post when it looked easier to score, while Adam Bartlett saved well from Drewe Broughton before Kevin Ellison directed a header wide from just outside the six-yard box.
Hereford finished strongly though, and Pugh added a third with a fine run and strike into the corner of the net in the 90th minute.