'Best side won,' says beaten Rotherham United boss Paul Warne
The Millers gave as good as they got up until the interval then tired following their efforts against AFC Bournemouth at the weekend and conceded two goals.
"I thought we were really good in the first half, as good as we could be really," manager Warne said. "We limited them to very few chances and worked really hard out of possession.
"We created a few half-chances that, if you're going to beat a top team, you have to take. Brentford were better than us after the break.
"They had that little bit of class that we didn't."
Bees boss Thomas Frank, whose side are up to fourth in the Championship after eight games unbeaten, admitted his men had been given a tough game before Marcus Forss scored in the 57th minute and Ivan Toney despatched an 82nd-minute penalty.
Rotherham substitute Mickel Miller conceded the spot-kick and was sent off 11 minutes after coming on for a second booking.
Frank said: ""It was a very good win and a mature performance. The first half was too open for my liking. They created a few counters. They are very difficult to play against.
"Second half, I thought we were unbelievable. We gave nothing away defensively and on the ball we went up a level."