Earl made his NHL debut as a Toronto Maple Leaf in their game on February 2, 2008 versus the Ottawa Senators. He recorded an assist.
Earl began his hockey career playing with the Wisconsin Badgers in the NCAA. In his freshman season on 2003-04, Ear scored 27 points, and was named to the All-Rookie team. He also received Player and Rookie of the Week awards during the season. While playing with the Badgers, Earl scored a goal in the final of the 2006 Frozen Four tournament against the Boston College Eagles, helping the Badgers win the NCAA Men's Hockey Championship. Robbie also scored twice against the University of Maine Black Bears in the Frozen Four semifinal. He was selected 187th overall by the Toronto Maple Leafs in the 2004 NHL Entry Draft.
Earl began his professional career in the AHL with the Marlies. He played one game during the 2005–06 regular season with the Marlies without registering any points or penalties. Earl also saw action in the team's first round North Division semifinal series against the Grand Rapids Griffins in the 2006 Calder Cup Playoffs. The following year, he scored 12 goals and 18 assists and racked up 50 penalty minutes while playing in 67 games with the Marlies. In the 2007-08 season, Earl had his best AHL season to date, scoring 14 goals and 47 points in 66 games.
On February 2, 2008, Earl made his NHL debut with the Maple Leafs in a game against the Ottawa Senators. Earl recorded his first NHL point, an assist, in that game. Earl went on to play eight more games with the Maple Leafs that season, but failed to record another point.