The summer signing from Crewe ended his mini-goal drought in style with two super strikes to sink the Yorkshire side.
Hulse made a flying start to the season with nine goals but when dried up and failed to score in six. But his two second-half efforts came after a Shaun Barker own goal gave Albion a helping hand.
Albion could have trailed after only 12 minutes when Paul Warne came close to an opener for Rotherham but his 25-yard volley was saved superbly by keeper Russell Hoult diving full stretch to his left.
The Millers found West Brom midfielder Jason Koumas a handful but when he produced a clever chipped effort Mike Pollitt saved with ease.
And once West Brom found their feet they eased into the driving seat and pinned back the home side.
Rob Hulse went close with a diving header before Lee Hughes glanced a header wide and Chris Sedgwick has to block on the line when Thomas Gaardsoe headed a Koumas corner.
But West Brom needed a slice of good fortune as they edged in front after 39 minutes. Bernt Haas picked out Koumas who drove in a low cross that Shaun Barker diverted past his own keeper.
Hulse then produced his first four minutes into the second half. As the Rotherham defence backed off he picked his spot and lashed a 25-yarder past Pollitt.
His carbon-copy second came after 65 minutes when Darren Byfield gave away the ball cheaply as Rotherham looked for a way back.
The ball broke to Andy Johnson and he picked out Hulse who punished the home side with another accurate long-range shot to take his tally to ten for the season.
Rotherham: Pollitt, Shaun Barker, Swailes, McIntosh, Minto, Mullin, Talbot, Sedgwick, Warne, Byfield, Richard Barker. Subs: Montgomery, Robins, Hurst, Monkhouse.
West Brom: Hoult, Haas, Robinson, Gilchrist, Gregan, Gaardsoe, Koumas, Johnson, O'Connor, Hulse, Hughes. Subs: Clement, Wallwork, Dobie, Sakiri, Murphy.
Referee: A Butler (Nottinghamshire).