Jordan Hugill is Preston's top scorer with seven Championship goals this season
Rotherham's winless run was extended to 12 games as first-half goals from Jordan Hugill and Callum Robinson helped Preston to a comfortable win.
Robinson spurned a great chance before Hugill headed in off the post from Greg Cunningham's cross to open the scoring.
It was 2-0 when Aiden McGeady teed up Robinson for a tap-in from close range.
Substitute Peter Odemwingie crossed for Richard Wood to halve the deficit with a header, but Marnick Vermijl tapped in to seal the win on the counter-attack.
Rotherham are now without a win since 20 August and are eight points from safety at the bottom of the Championship.
Joe Mattock and Jon Taylor threatened for Kenny Jackett's side with long-range efforts, but the former Wolves manager has just one point from his opening four matches in charge.
Preston, meanwhile, responded perfectly to last week's 2-1 loss to Newcastle to move up a place into 11th with a fifth win from their last last eight matches.
It could have been an even bigger scoreline, but Robinson failed to make a proper connection from a McGeady cross and then smashed an effort from the edge of the box narrowly wide.
Rotherham manager Kenny Jackett: " "It's deflating for the players because you need to stay in games.
"We didn't do enough and we didn't have a defensive solidity about us that could keep us in the game.
"I am learning about the players and trying to find the best combination for us.
"We have quite clearly given away far too many goals this season. Since I've come in, we have conceded six goals in three games and it's very difficult to get points under those circumstances."
Preston manager Simon Grayson: " "We warned the players about Kenny being new to the club and him being desperate to get out of the run they have been on.
"We were professional and started the game well. We played some good stuff but also mixed it up and battled and scrapped when we had to do.
"I was really pleased with the individual and the team performance. It was a professional performance from us.
"We are pleased with how we are progressing but we won't get carried away. We will just keep plodding away and see where it takes us. Anything could happen for any club in this division because it's relentless."
