Holmes hit the first hat-trick by a Rotherham player since Deon Burton's treble over Blackpool in 2005 by netting two tap ins and a free header.
"I happened to get in the right place at the right time but we have been working at it and it's only my second hat-trick, It seems to be that I'm at the back post every time I score, but it's important to get in the right place.
"To be fair, I got great service for the goals and the other lads up there with me (Chris O'Grady and Ryan Taylor) put in a lot of work."
The Millers remain unbeaten on the road since their only league defeat away from Millmoor to Barnet on 29th September last year.