Thomas Frank hailed his Brentford side for breaking down stubborn Rotherham but warned they can still improve.
Marcus Forss and Ivan Toney scored in the second half as the Bees climbed to fourth in the Championship, two points off the top.
Frank, quoted by westlondonsport.com, said: "I am very pleased with the result. I must praise Rotherham, who made it very difficult for us – especially in the first half when we struggled to create anything.
"Also we gave away some good opportunities for them, but we hung in there and played a lot behind Rotherham. In the second half I thought we were in control more or less throughout and scored two very good goals.
"It was a very pleasing performance with again a lot of attitude, hard work, and togetherness, but I still expect us to get another level – on the ball we need to be better.
"Keeping five clean sheets is massive and very difficult in this league, so the boys deserve a lot of praise.
"But we next face Blackburn, who are maybe the best offensive team (in the division) at this moment in time. I think they are amazing, so I think that could be our toughest test defensively but we'll be ready for it."
The Bees opened the scoring in the 57th minute when Forss fired home from 12 yards after being fed by Toney following Bryan Mbeumo's cross.
Toney then notched for the 13th time this season with a penalty eight minutes from time after Rotherham substitute Mickel Miller was sent off for hauling down Sergi Canos.
Millers boss Paul Warne told his club's website: "I haven't got too many complaints, I know defeat stings no matter what.
"We were carrying a few injuries and massive fatigue from the weekend but I thought first half we were excellent, the best we could be.
"We probably didn't create enough clear-cut chances to take the lead but I thought we were the team in the ascendancy, I don't think my keeper had anything of note to do first half.
"Second half they got a bit more of a stranglehold, they were the better team. A bit of class for their first goal, they put the ball down the side, hit a good pull-back, good finish. Unfortunately we couldn't match that.
"We were trying to get back into the game, we weren't just trying to sit back, and got done with a sucker punch and obviously with the sending-off for Mickel, and then it was game over really.
"It doesn't detract from how proud I am of the performance and how we tried to take it to another top team."
