Leading goalscorer Le Fondre officially signed for Reading shortly before the kick-off, but the home side provided their fans with just the tonic they needed.
Chances were at a premium in a goalless first half but both teams went very close to making a breakthrough.
Strong and very mobile going forward, Gillingham posed problems and after 29 minutes only a brave save by Conrad Logan denied Danny Kedwell.
Kedwell had another chance after 38 minutes but his pile-driver from the edge of the area was well wide, while Curtis Weston's 30-yarder also whistled past the post.
At the other end it was Gareth Evans leading the Rotherham charge. His 31st-minute shot was blocked by Jack Payne and nine minutes later his goalbound effort was brilliantly turned round the post by Ross Flitney, who denied the same player again just before the break.
But a rampant Rotherham upped their gears and went infront eight minutes into the second half. Danny Schofield's trickery out on the right earned him the chance to cross and Danny Harrison headed home off the inside of the upright.
Ten minutes later Rotherham doubled their advantage. A peach of a throughball from substitute Mark Bradley picked out Lewis Grabban and he fired home from just inside the area.
And the home side's second-half romp was completed in the 78h minute when Marcus Marshall's pin-point right wing cross was drilled home by Evans to take the Millers back to the top and end the visitors unbeaten start.
Source: DSG