The midfielder was a target for Tottenham 12 months ago.
Rosenior told EFL Championship Goals, Grealish was “for sure" one of the best outside of the top flight.
He said: “As an attacking midfield player, him and Mason Mount. They're so creative, they get goals, Jack's been an absolute revelation this season.
“Credit to him because Tottenham came in for him and a lot of players would have really pushed the move.
“He didn't really get his move, but he's dragging a huge club back to where they should be which is in the Premier League."