The 30-year-old registered one assist and 10 penalty minutes in 17 games as an assistant captain with Carolina this season.
Gleason has played 616 games in his NHL career with Carolina and the Los Angeles Kings, collecting 15 goals and 113 assists for 128 points, with 591 penalty minutes.
He was originally drafted 23rd overall by the Ottawa Senators in 2001 NHL Entry Draft.
Liles, 33, played in just six games with the Leafs this season and recorded 15 hits, 10 blocked shots and averaged 17:03 of ice time per game.
The Indianapolis, IN, native also skated in 16 games with the Toronto Marlies of the American Hockey League, scoring three goals and adding 10 assists for 13 points.
"John-Michael is a puck-moving defenseman who has demonstrated in his career that he can make a difference offensively from the blue line," said Hurricanes GM Jim Rutherford.
"Tim has been a valuable player and leader for the Hurricanes for a long time. We thank him for the contributions he has made to the team and the community and wish him all the best as his career continues."
The Colorado Avalanche drafted Liles in the fifth round, 159th overall, in the 2000 NHL Entry Draft.
Liles has notched 77 goals and earned 236 assists (313 points) in 627 NHL regular-season games with the Avalanche and the Maple Leafs.
Robertson, 22, is in his senior season at Brown University and leads club defensemen with eight points (3g, 5a) in the Bears' 12 games this season.
The Maple Leafs drafted Robertson in the sixth round, 173rd overall, in the 2011 NHL Entry Draft.