A controversial goal from Danny Ward condemned Brentford to defeat in south Yorkshire.
The Millers striker was deemed to be onside when he latched onto a through ball and he curled it past Dan Bentley to give the home side the lead, although there also appeared to be a foul on Scott Hogan in the build-up.
Despite, Dean Smith's side applying plenty of pressure they were unable to breach a stout Rotherham defence, who had nine players defending the edge of their penalty area. Scott Hogan and Lasse Vibe were both guilty of fluffing their lines when they had a chance.
Below are the talking points to take away from the Bees' second league defeat of the season.
Scott Hogan will be disappointed with his performance at the New York Stadium after being unable to look like scoring.
The striker's balance let him down on occasions and, when he did have a shot, it was easy for Lee Camp to deal with.
Lasse Vibe looked ring rusty to the demands of Championship football after returning from the Rio Olympics.
He showed flashes of the form he displayed at the end of last season and I'm certain he will return to that level in a short time.
No hope for Hofmann?
Philipp Hofmann was left out of the matchday squad with Dean Smith opting not to have a recognised striker on the bench.
The Bees head coach believed that he had Scott Hogan and Lasse Vibe who could do a job in that role, while Romaine Sawyers or Emmanuel Ledesma could also perform up there.
Neither former Walsall men regularly play as a striker so it appears that the German U21 international is a long way down the pecking order.
The club won't say it officially, but it would not be a surprise if Hofmann leaves the club this month in order to get game time.
Ledesma looks for deal
Emmanuel Ledesma was given 15 minutes to try and help Brentford find an equaliser and he showed glimpses of his potential.
While the sight of a non-contract player gracing the Championship reflects badly on the Bees' transfer business this summer, the Argentine showed he may well be worth a contract at the club.
His delivery from dead ball situations was excellent and he showed desire tracking back as well as he tried to impress the powers that be he merits a deal.
You get the feeling, though, that he may be seen as plan B if other targets fail to materialise.
Dan Bentley was, once again, excellent in the Bees' goal and could do nothing about Danny Ward's winner.
The former Southend man made what has almost become a trademark save from a one on one when Izzy Brown raced through after dispossessing Lasse Vibe. That followed his save from Britt Assombalonga on Tuesday that earned the Bees two points.
When Ward had his one on one for the goal, there was almost an expectation that the goalkeeper would pull it off again.
David Button was excellent during his three years with the club but Bentley may yet prove to be an extra step up in class.
Ryan Woods was, by a comfortable margin, Brentford's best player at the New York Stadium.
The former Shrewsbury man had the nickname 'the Ginger Pirlo' during his time at New Meadow and it was almost like watching the legendary Italy midfielder at times.
He had a sat-nav of the New York Stadium logged in his head with every blade of grass memorised and picked out some inch perfect passes.
The pick of them was to Maxime Colin on the right hand side which perfectly split the defence.
He has formed a good partnership with Nico Yennaris and it is going to take something special for Josh McEachran and Alan McCormack to get back into the team.
Lewis Macleod is fit and firing and has already caught the eye in the Championship this season with his performances for Brentford.
His ball striking skills are exemplary and he also has a fierce shot on him. It has been good to see him ride through a few knocks after 18 months of niggling injuries.
As he adapts to the rigours of the Championship further, expect the Scot to become a key player for Dean Smith's side.