Reid made it 10 in his last 10 games – and 19 for the season – with a smart finish from Pablo Mills’ pass.
It was the visitors who made all the early running and Myles Weston slammed a shot against the crossbar after only six minutes before Jonathan Forte had Rotherham goalkeeper Andy Warrington at full stretch to turn his shot for a corner.
Ian Sharps had a goal disallowed for the home side in the 39th minute for a foul, but five minutes later they led when Micky Cummins threaded a delightful ball through the visiting defence and Mark Hudson raced through to score.
Rotherham almost had a second but Reuben Reid’s close range shot was brilliantly blocked by Jamie Clapham’s challenge – but he made no mistake after 69 minutes to double the lead.
Forte put the cat among the pigeons with 15 minutes to go when he brushed aside Nick Fenton chasing a long ball and fired past Warrington but the Magpies could not find a leveller.