The ruling, which came after Belgian player Jean-Marc Bosman won a court case with UEFA, allows players to join another club on a free transfer at the end of their contract without commanding a fee.
It has made the movement of players much more fluid and a godsend for Steve Evans!
Here we look at some of the best and worst free transfers the Millers have made in the last 20 years.
The best
Mike Pollitt
The goalkeeper had two spells with the Millers, with a year at Chesterfield in between, but he originally arrived in 1998 on a free transfer. He had a fine debut season as the Millers missed out on promotion in the play-offs before playing a key role in automatic promotion from Division Three the following season. He left on another free to the Spireties before the Millers bought him back for around £70,000 the year after.
Lee Williamson
Arriving in the summer of 2005 on a free from Northampton, Lee Williamson was the stand-out player in a Millers side which was struggling following their relegation from the Championship. He had a consistent 18 months and was sold to Watford with Will Hoskins for a joint fee of £1million as the club battled financial trouble.
Ben Pringle
One of Andy Scott's best things as Millers manager was to get Ben Pringle to join on a free transfer in 2011, but then decided not to use him. It was Steve Evans that "got him out of the cupboard" and the former Derby man was a key player for three seasons as the Millers rose from League Two to Championship safety. He left in the summer for a move to Fulham.
Kieran Agard
Another one of Evans' master strokes was to offer Agard a deal in 2012, though the Millers had to wait until the end of that season for him to come good as a number of goals helped fire them to promotion. It was in the 2013-14 campaign where he made his mark as his 26 goals sent the Millers to an unlikely second successive rise. He was sold last August for a fee that is believed to have gone up to £1million.
Kevin Watson
Ranked as one of Ronnie Moore's best signings by the man himself, Watson came to the Millers in 1999 on a free after Moore and John Breckin persuaded the London boy to come north. And it was inspired as he captained the Millers to successive promotions to Division One and was a real key cog. He soon become the target of boo boys, though, and was sold to Reading for £150,000.
Lewis Grabban
Another one of Scott's positives was that he brought Lewis Grabban to the club in 2011. And the former Brentford and Millwall man was a star performer in a turgid side, scoring 21 goals in 47 appearances. However, northern life wasn't for Grabban and he wanted a move back home, so was sold after just one season, with the Millers making a cool £300,000 profit.
The worst
Mat Sadler
The epitome of Evans' scatter gun approach to his summer recruitment following promotion to the Championship, Sadler arrived at New York Stadium on a free in 2014. After playing just 90 minutes in the League Cup, the left-back had two loan spells away from the club before having his contract terminated in the summer.
Laurie Wilson
Wilson arrived from Morecambe in 2012 as Evans plotted a promotion campaign and started the season as first-choice left-back but paid the price for his part in the 6-2 defeat to Port Vale. And despite a host of loan left-backs dropping injured, he was never chosen again and left for Accrington just a few months into the season.
Danny Hylton
Seemingly signed on the back of a hat-trick he scored against the Millers the previous season, Hylton arrived at New York in the summer of 2013 on a free from Aldershot. However, he made just two appearances, had a loan spell at Bury and left after just one year of his two-year deal.
Paolo Vernazza
Supposedly a player of better quality as the Millers strived to establish themselves as a second-tier club under Moore, Vernazza signed from Watford in 2004. But his arrival was the opposite of what had got the club to that level and his 30 appearances were a key reason in the club going down, with his most famous contribution a comical own goal in a defeat at Gillingham. He left early into his second season at Millmoor.
But there is only one Bos Man!
The bleached-haired, white-booted Dutch striker was signed by Moore in 1997 and has become a cult figure at the club, owing to how bad he was. But unbelievably, he cannot be included in this feature because the Millers paid £20,000 for him!
