Preston had only scored four goals before Tuesday's game and have now trebled that total in two matches.
In contrast poor Rotherham have only scored two goals in their eight games and conceded 16.
Preston opened the scoring after 11 minutes when Richard Cresswell latched onto Michael Keane's pass before hitting a ten-yard shot home.
Rotherham had an early chance when Darren Byfield saw his goalbound effort pushed round the post by Jonathan Gould while at the other end Ricardo Fuller's great run was ended when Mike Pollitt saved well.
Right on half time, loanee Carl Robinson's cross was headed home by former Preston player Byfield. There was a suspicion of offside but Graham Alexander appeared to play him on.
Fuller scored his fifth goal of the season after 55 minutes. Cresswell knocked the ball down to Keane whose shot from the left was saved. However, Fuller picked up the rebound on the right and hit a close-range shot into the top corner of the net.
Preston made it 3-1 in the 63rd minute when Shaun Barker brought down Cresswell and Alexander slotted home the penalty. Barker was sent off for his challenge.
Brain O'Neil capped a fine team performance with an acrobatic 73rd minute goal when he scissor-kicked a volley over Pollitt into the net after good play by Alexander and Chris Lucketti.