Hammers captain Christian Dailly led by example to head his team to the second half victory that leaves them just one place and two points away from the play-off berths.
When West Ham lost at Rotherham back in August amidst controversy over their supposed refusal to change in the cramped Millmoor dressing rooms, that defeat signalled the end of the road for Glenn Roeder.
Five months on, it was all change for the Hammers again as new boss Alan Pardew's recent transfer dealings meant that only four of the East Enders' starting line-up had survived from the eleven who trotted out for that Millers mauling.
While West Ham had an abundance of new riches, poor Rotherham could only name four substitutes.
And the eleven Yorkshiremen out on the pitch were soon under pressure too, as Mike Pollitt was forced to deny both Brian Deane and David Connolly.
On the quarter hour mark, however, the Rotherham keeper could do nothing as Deane climbed highest in the six yard box to powerfully nod home Michael Carrick's well-flighted corner.
Midway through the half, though, West Ham were left stunned as Chris Sedgwick's right-wing cross was met by the diving Richard Barker and while Stephen Bywater did well to parry the heavily bandaged Tomas Repka could only slice an attempted goal-line clearance into his own net.
Having now surrendered the lead for the eleventh time in their last eighteen league outings, the Hammers were now struggling to break down a visitors side packing men firmly behind the ball.
As the hour mark approached though, the Rotherham resistance was broken when skipper Dailly met Matthew Etherington's corner into the six yard box with a thumping diving header.
West Ham were now firmly in control and on 73 minutes Nigel Reo-Coker almost capped a sparkling debut with a cracking low 18 yarder that Pollitt did well to hold, before he unluckily struck the far post with an angled shot a few minutes later, but by then the Hammers had already done enough to secure a deserved victory that lifted them up to seventh spot in the table.