Albion moved to within two points of the automatic promotion places thanks to a hattrick from Dwight Gayle and another from Harvey Barnes.
Here's our ratings as Albion kept only their second clean sheet of the season:
Sam Johnstone: Will be delighted with a rare shutout. Had the post to thank and a Craig Dawson goalline clearance to thank for his clean sheet bonus. 6/10
Tosin Adarabioyo: Did well to set up Gayle's third but had earlier conceeded a needless penalty. Mixed afternoon. 6/10
Craig Dawson: Fantastic anticipation to make his goal line clearance during a rare Rotherham opportunity. Pretty much solid throughout. 7/10
Ahmed Hegazi: Didn't need to get out of second gear but was still happy enough to throw his body in the way when required. 7/10
Kieran Gibbs: Not as threatening going forward as in recent weeks but still did his duties up and down the pitch. 6/10
Gareth Barry: Carried on where he left off at Bramall Lane. Kept it simple and pushed Albion forward. 6/10
Jake Livermore: Another who didn't need to get into top gear but broke up play when required. 6/10
Matt Phillips: See Barry and Livermore. Didn't really impact the game as we know he can. Subbed late on. 6/10
Dwight Gayle: Free kick, header and tap in. Not quite the perfect hattrick but the perfect performance. 9/10
Jay Rodriguez: Will be kicking himself he only hit the post when it seemed easier to score. Luckily his rebound found Barnes for an easy tap-in. 6/10
Harvey Barnes: Is he now Albion's most influencial player? One goal this week after two assist last time. Let's keep everything crossed he isn't recalled in January. 7/10
SUBS
Chris Brunt: Came on after an hour for Barry and maintained Albion's foothold in midfield. 6/10
James Morrison: A welcome return for Mozza and he picked up where he left off before his injury. 6/10
Hal Robson-Kanu: Another who was making up for lost time. Did well to hold up the ball and kill off the game late on. 6/10