Titans threw away an 18-12 half-time lead, built on the foundations of solid work from the pack, to crumble and gift the visitors four points which will give them a massive lift in their drive to escape the bottom four play-off scramble.
Bester's men are now one point ahead of Plymouth but with two games in hand but, despite the setback, the coach says his side won't be dragged into trouble.
"It was a disappointment but where we finish is in our own hands," he said.
"We still have the other bottom teams to play and if we win those games then we will be in the promotion play-offs. We've always said that our intention is to finish in the top eight and we'll then take it from there."
But he knows Rotherham will have to up their game, especially after the second-half performance which saw Albion boss possession.
The visitors had led after only three minutes, when David Copeland battered his way through flimsy cover tackling to score under the posts, Alex Davies making it 7-0.
Titans hit back with two Juan Pablo Socino penalties, only for Albion to notch their second try when wing Cameron Mitchell touched down in the corner.
Rotherham's pack grabbed the initiative as skipper Joe Bedford burst through and then Ryan Burrows squeezed over the whitewash to put Bester's side in command at the break.
But Albion went back in front as Mitchell finished off a sweet cross-kick from Davies to plant the ball down in the corner, Davies converting to make it 19-18.
Titans nosed back in front with a third Socino penalty but when Davies clubbed a pressure-packed three-pointer with two minutes to go it made sure the win points were on the way to Devon.