The 22-year-old central defender put pen to paper on a two-year deal with the Millers on Friday following his release from Manchester United, where he was tipped to excel.
Evans said of his sixth summer signing: “This is a young man that I have targeted since the first day he was released by Manchester United.
“There is no secret within the Millers that I tried to take young Tom on loan on a number of occasions last season, but at that time we couldn’t make it happen.
“This young man has everything that is good with the modern day footballer. He has height, strength, speed, awareness and technical ability.
“There is no doubt that this lad for me is exceptional, and we are delighted to be able to attract a player who has had multiple options to sign for clubs in the Premier League, Championship and Scottish Premiership.”
Thorpe, who made one senior appearance for the Red Devils and spent time on loan at Birmingham in 2013-14, is the sixth summer arrival at the Millers.