A solid and confident display from the Millers ensured a winning start to their Carling Cup campaign against Championship rivals Derby County.
Despite the Rams taking the lead on 10 minutes through Gary Teale, Rotherham responded with a strong attacking spell finished with a Paul Warne goal, his second of the season.
The home side continued to show assurance despite playing against higher-tier opposition and grabbed a second through Kevin Ellison on 63 minutes after a superb build-up move. The goal crowned a deserved victory for Rotherham, who looked a classy and comfortable outfit throughout.
Rotherham started the game brightly, taking the initiative in the opening minute when some good link-up play between Tom Pope and Nicky Law on the left created a chance shot just wide from Warne.
The Millers continued to look the brighter in what was a fast paced opening; however Derby broke through on 10 minutes with Lee Croft picking up a through ball to see him in behind Rotherham's defence. Croft then coolly squared the ball to Teale who slotted home to take a 0-1 lead to Derby.
The game then became a battle fought in midfield, with both Robbie Savage and Pablo Mills looking lively, with Mills striking a low hard shot just wide from 25 yards in the 21st minute.
Derby though settled down noticeably after scoring with centre backs Miles Addison and Jake Buxton dominating the aerial battle while Savage, playing the holding role, controlled and distributed the ball with precision.
However Rotherham maintained the pressure and they were rewarded after Ian Sharps won the header from a Nick Fenton cross to put Warne though, with the veteran striker stretching to slot past a helpless Steven Bywater.
Rotherham United 1-0 Derby County
Both sides continued to look lively into the second half, with Luke Varney starting to look threatening to the Millers defence, though it was again Warne and Mills who provided inspiration to the home side.
The Millers continued to press and broke through in the 63rd minute when Ellison crowned a precise passing spell, calmly finishing from 10 yards after being set up by the enigmatic Law.
Derby responded well to conceding and started to show some of their Championship class, with Fenton forced to head clear off the line. A dogged spell followed but Rotherham held on and proved they were not prepared to be overwhelmed by the Rams.
The Millers continued to force Derby back but the two minutes of stoppage time proved a nervy affair for the home side, with Dean Moxley fizzing a low shot just wide. Andy Warrington then demonstrated his class by saving as James McEveley was through only to hit straight at the imposing Warrington who was strong to deny the away side in the closing minutes.
Rotherham United 2 v 1 Derby County
Rotherham: Warrington; Tonge, Sharps, Fenton, Green, Law, Mills, Taylor, Ellison (Liddell 69), Pope, Warne.
Subs not used: Annerson, Joseph, R. Taylor, Harrison, Lynch, Cummins.
Derby: Bywater; Connolly, Addison, Croft, Savage, Teale, Pearson, Buxton, Pringle (McEveley 79), Davies (Varney 14), Moxey.
Subs not used: Leacock, Deeney, Barker, Mendy.
Report: Matthew Parr