Goals from Derek Holmes and Mark Hudson left Chesterfield empty handed once again at home, but they could have no complaints about the result on a difficult night for both teams.
A strong and swirling wind presented problems for the players, but Rotherham coped better with the conditions and their defence, superbly marshalled by Graham Coughlan, restricted Chesterfield to only a couple of openings.
They might have been in front as early as the fourth minute when Stephen Brogan appeared to be tripped inside the area by Derek Niven, but a mistake by Barry Roche allowed Derek Holmes to put the visitors ahead.
Roche fumbled a 25-yard shot from Chris O'Grady and Holmes reacted quickly to fire into the roof of the net.
Chesterfield came close to an equaliser when Adam Rooney broke away and set up Jamie Ward whose shot on the turn from 20 yards was only just wide, but Rotherham always looked capable of inflicting further damage.
With Pablo Mills presenting a muscular presence in the midfield, Chesterfield struggled to create space for the frontmen and once Rotherham scored again, the game was over.
The second goal arrived when substitute Peter Holmes crossed from the left and O'Grady headed down for Hudson to score from ten yards.
Chesterfield made a double substitution to try and disrupt Rotherham's gameplan, but once Steve Fletcher had headed wide from a cross by Phil Picken, there was only going to be one winner.
Rotherham threatened to score more goals on the break but they had already done enough and on this showing should be among the teams challenging near the top of League Two at the end of the season.