2009-10: Alex Roach skated in four games for the Quesnell Millionaires of the BCHL while spending the majority of the season with the Cariboo Cougars in British Columbia midget hockey. He had no points and 2 PMs in limited action with the Millionaires. In 40 games with the Cougars he scored 6 goals with 15 assists and 68 PMs and had 2 assists with 16 PMs in four playoff games. Roach was selected for the 2010 Major Midget League All Star Game.
2010-11: Roach skated in 61 games for the Calgary Hitmen in his first season in the WHL. After starting the season as a healthy scratch and then seeing some time at forward to get acclimated to the faster page of major junior hockey, Roach was logging significant ice time for the Hitmen and attracting the attention of scouts with his physical play. Roach finished with 4 goals 12 assists and was -24 plus/minus (Calgary had the WHL's worst record and won just 20 games) with 77 PMs. Ranked 142nd amongst North American skaters in Central Scouting's final rankings, Roach was not selected in the 2011 NHL Draft but was invited to the Kings camp and signed a three-year, entry-level contract with Los Angeles in September, 2011.
2011-12: Roach returned to Calgary for a second season of junior hockey with the Hitmen after his impressive performance in Kings camp. On a much-improved Calgary squad he put up nearly identical offensive numbers to the previous season – scoring 4 goals with 18 assists (two more assists than in 2010-11). Three of his 4 goals were scored on the power play and he finished with 78 penalty minutes. Calgary went from last place to second in the Central Division and Roach's plus-minus reflected that improvement: he was plus-eight after finishing minus-24 the previous year. He scored 1 goal with 2 assists and was minus-one with 2 penalty minutes in the five game playoff series with Brandon.