Previously a head coach at Southern Methodist University, Rossley started his coaching career in 1969 at the high school level. After serving as a graduate assistant coach at the University of Arkansas in 1972, Rossley worked as an offensive assistant coach at one high school and several colleges. These coaching jobs were at Lake Worth High School, the University of Cincinnati (his alma mater), Rice University, Holy Cross, and Southern Methodist University, respectively. He also spent time coaching in the Canadian Football League, Arena Football League, and the now defunct United States Football League. While at Holy Cross, Rossley worked with future Green Bay Packers Head Coach Mike Sherman, where the two became friends and established a successful working relationship. Rossley's job at Southern Methodist led to the head coaching position, after a one-year forray into the NFL, where he worked as a quarterbacks coach for the Atlanta Falcons in 1990. From 1991 until 1996, Rossley was the head coach at SMU, earning Co-Coach of the Year honors in the Southwest Conference for impressively turning around the 1-10 Mustangs with a respectable 5-6 record in 1992. After leaving the Mustangs, Rossley spent two years as an assistant with the Chicago Bears and one year with the Kansas City Chiefs before being offered the Packers offensive coordinator position in 2000 by his old friend Mike Sherman, who was at the time putting together his first Green Bay coaching staff.
In early 2006, Sherman was fired by the Packers after a disappointing 4-12 season. The new head coach, Mike McCarthy released much of the coaching staff after he was hired, including Rossley.