Alex Revell scored both of Rotherham's goals as the Millers beat Tranmere to consolidate their place in the League One play-off spots.
An early strike by visiting striker Wes Thomas was disallowed for offside but Rotherham did go in front when Revell turned in Kieran Agard's cross.
And Revell doubled the lead with a shot from the edge of the penalty area.
Veteran midfielder Andy Robinson ensured a tense finish when he headed a late reply but Rovers fell to defeat.
VIEWS FROM THE DRESSING ROOM
Tranmere manager Ronnie Moore told BBC Radio Merseyside:
"I thought we were abysmal. I'm disappointed with the commitment and desire.
"We played for five minutes right at the end and it's not good enough. I expect them to run about and show some desire, but nearly every one of them was giving the ball away with simple passes.
"If we play anywhere near where we can play, at least we give them a game. I don't think it was a game."
Rotherham manager Steve Evans told BBC Radio Sheffield:
"It could have been four or five but it wasn't.
"It's a good day for us. It's a difficult place to come for us, on a difficult surface against a team that's very organised.
"We came with a game plan for stages of the game and they carried the game plan we worked on from Sunday."
Tranmere Rovers 01 Williams 29 Pennington 03 Horwood 18 Jennings (Koumas - 74' ) 04 Taylor 32 Arthurworrey 20 Kennedy (Stockton - 78' ) 08 Wallace 14 Cassidy 09 Lowe 15 Kirby (Robinson - 59' ) Substitutes 02 Holmes 05 Goodison 10 Robinson 16 Stockton 17 Power 22 Koumas 33 Mooney Rotherham United 21 Collin 14 Bradley 27 Tavernier 08 Frecklington (Vuckic - 88' ) 05 Davis 04 Arnason 22 Agard 15 Milsom (Smallwood - 71' ) 09 Revell 26 Thomas (O'Connor - 81' ) 18 Pringle Substitutes 03 Skarz 10 O'Connor 16 Turgott 28 Vuckic 30 Thompson 35 Hitchcock 36 Smallwood
Ref: Steve Bratt