Ronnie Cottrell played football at T.R. Miller High School, graduating in 1977. Cottrell began his collegiate education and was an assistant at his alma mater for a year. He then continued to Troy University, where he was a student assistant from 1981-82 coaching with Charlie Bradshaw.

Upon graduation, he received his first head coaching job at Kinston High School. After a 2-9 debut season, Cottrell led the Bulldogs to only their second winning season in school history in 1984 at 6-4, which is still tied for the program's best record in a season. Following that year, Cottrell returned to his home of Escambia County to lead the Flomaton Hurricanes. During his first season, the Hurricanes posted a 6-5 record and made their first playoff appearance in school history. Cottrell followed that up with back-to-back 10-0 regular seasons in 1986-87, the first in school history, finishing with records of 11-1 and 12-1 in those years. Cottrell then moved on to W.S. Neal High School, where he led the Blue Eagles to a 6-5 record and a playoff appearance in 1988.

Following that season, Cottrell took an opportunity as a graduate assistant at Florida State University under legendary coach Bobby Bowden. After a year as a G.A., Cottrell was promoted to recruiting coordinator, where he would go on to post several highly-ranked classes, including the No. 1-ranked class by SuperPrep in 1993. He was promoted to an on-field assistant in 1994, and spent his final four years with the Seminoles coaching middle linebackers, tight ends and special teams. During his time in Tallahassee, he recruited such notable players as Derrick Brooks, Warrick Dunn and Peter Boulware. Cottrell also served on the FSU staff with future college head coaches Brad Scott, Mark Richt and Chuck Amato. The Seminoles won a national championship in 1993 and six ACC championships during his time there.

After nine years at Florida State, Cottrell joined Mike DuBose's staff at the University of Alabama as assistant head coach, recruiting coordinator and tight ends coach in 1998. Cottrell recruited future NFL stars Antwan Odom, Jarrett Johnson and Kenny King to the Crimson Tide during his three years in Tuscaloosa, which included an SEC championship win in 1999.

After spending a few years out of coaching following DuBose's staff's dismissal in 2000, Cottrell rejoined the high school coaching ranks in 2005 at Carroll High School in Ozark. The Eagles went 7-4 in his debut season with a second-place finish in the region. He resigned following a 2-8 record in his second season in Ozark. After taking another year off from coaching, Cottrell led Alma Bryant high school for two seasons, posting a 7-13 record.

Cottrell then returned to Tallahassee, taking the helm at A.P. Godby High School from 2010-13. There he compiled a record of 38-13, reaching the playoffs all four years and winning his first high school state championship in 2012 with a record of 14-1. Following that, Cottrell returned to Alabama to lead Chickasaw High School's very first football team. He led the Chieftains to a 4-7 record and a playoff appearance in that inaugural season before moving on to co-coach at Mobile Christian alongside Tommy Wasden in 2015. The Leopards went 10-2 that season before he took over as full-time coach in 2016, leading the Leopards to a 13-2 record and their first appearance in an AHSAA state championship game.

His Leopards won the 2023 3A state championship with a huge victory over Madison Academy in Tuscaloosa.