Manager Ronnie Moore brought in two new loan players in the week, forward Craig McAllister from Exeter, who went straight into the opening line-up, and winger Abdulai Bell-Baggie from Reading who made the bench.
There was a start for Marcus Marshall on the wing, coming in for injured Nicky Law.
The Millers got off to a bright start, with the Daggers struggling to get out of their own half, but the possession the Millers were enjoying was proving hard to turn into clear cut chances.
Kevin Ellison went close after with an overhead kick, only to find he was offside, and in the 36th minute Roberts in the Daggers goal tipped a shot from Josh Walker wide.
Marcus Marshall was making the most of his debut, with his speed proving to be a valuable asset.
Half Time 0-0
The second half the Daggers came more into the game with right winger Danny Green becoming a hand-full for Mark Lynch at full-back.
However that speed of Marshall and quick thinking paid dividends in the 60th minute when a cross from Marshall was not dealt with by the Daggers defence.
Nick Fenton had the initial shot which screwed to new signing Craig McAllister and his point blank shot was brilliantly saved by Roberts, only for the ball to go to Adam Le Fondre to tap in his 26th goal of the season.
The goal pressed the Daggers into pushing forward looking for an equaliser, and looked like they had got it when the dangerous Danny Green had his cross headed over by Phil Walsh.
Pablo Mills came on in the 80th minute to replace Kevin Ellison to add numbers to the defense, followed three minutes later by Dale Tounge replacing Mark Lynch, to bring a fresh pair of legs to cover Green.
The Daggers pressed in the four minutes of added time, but the Millers stood firm to take a much needed three points back to South Yorkshire.