Rotherham romped to a three goal lead in just 34 minutes, helped on their way by a 10th-minute own goal by Stockport debutant defender Aaron Brown, who headed Marcus Marshall's cross over his own goalkeeper.
12 minutes later, the Millers doubled their lead when Dale Tonge's hard low cross fooled everyone and Ryan Taylor tucked home a low shot from the edge of the area.
And in the 34th minute leading marksman Le Fondre ended a seven-game goal drought with his 18th of the season.
He waltzed through the offside trap on to a pass threaded through the County defence by Ian Thomas-Moore to slip his shot wide of the advancing Matt Glennon and into the empty net.
County's only shot of the first half came from Ishmel Demontagnac, but he skied his 39th-minute effort high over the bar.
Rotherham's fourth came in the 57th minute and owed a great deal to Le Fondre. He chased a lost cause to the by-line, the defender failed to put the ball out and Le Fondre crossed for Taylor to fire home his second.
Le Fondre should have had Rotherham's fifth when he fired home from 40 yards only to have the effort ruled out for a push and he then saw a six yard effort deflected for a corner.
Andy Warrington was called into action with a couple of smart saves but in truth the Millers climbed back into third spot at a canter ahead of Tuesdays game with Port Vale.