2009-10: Ryan Rehill played bantam hockey with the Maple Leaf Athletic Club in Edmonton and was selected by Kamloops in the sixth round (132nd overall) of the 2010 WHL Bantam Draft.
2010-11: Rehill appeared in four games with the MLAC's Midget 15AA team, registering 1 assist with 19 penalty minutes.
2011-12: Rehill played nine games with the Beverly Warriors junior B team and split the year between AA and AAA midget hockey in Edmonton. He had no points with 14 penalty minutes in six regular season games and had 1 assist and 16 penalty minutes in three playoff games for Beverly. Rehill scored 1 goal with 3 assists and 24 penalty minutes in 12 games with the Alberta Midget Hockey League's MLAC Maple Leafs. In 18 games for the SSAC midget AA team he scored 6 goals with 12 assists and 70 penalty minutes.
2012-13: Rehill was third on Kamlooops with 104 penalty minutes while playing in 46 of 72 games for the Blazers in his first WHL season. He had 3 assists and was +9 on one of the league's top teams. The Blazers finished second in the B.C. Division and reached the Western Conference finals. Rehill was -2 with no points and 8 penalty minutes in nine playoff games.
2013-14: Rehill displayed some offensive elements to go with his toughness in his second WHL season in a forgettable season for Kamloops. One of two Blazers to play in all 72 games, his 20 points were second to Josh Connolly (45) amongst Kamloops defensemen. He had 4 goals with 16 assists and was -4; leading the Blazers with 187 penalty minutes. Kamloops finished last in the B.C. Division with the WHL's third-worst record. Rehill was ranked 76th amongst North American skaters in Central Scouting's final rankings prior to the 2014 NHL Draft.