Selected eighth overall in the 2009 NFL draft, he spent the early years of his pro career with the Jacksonville Jaguars until a trade sent him to the Baltimore Ravens during the 2013 regular season.

Released by the Ravens in June 2016, Monroe announced his retirement from football one month later at the age of 29, citing concerns over head trauma sustained during his career.

Monroe is an outspoken advocate for the medical use of cannabis, and is noted for being the first active NFL player to publicly challenge league policy on the issue.

A two-time first-team All-State lineman, Monroe did not allow a quarterback sack in the last three seasons of his high school career.

As a true freshman in 2005 he appeared in all 12 games, serving as a backup to D'Brickashaw Ferguson at left tackle while also spending time at right guard.

He allowed zero sacks and only one QB pressure while leading the conference with 15 touchdown-resulting blocks, earning him an All-ACC mention from the league's coaches.

[7] Monroe was the third offensive lineman from Virginia selected in the top 15 of an NFL draft in four years, following D'Brickashaw Ferguson and Branden Albert.

In an effort to rebuild their offensive line, the Jacksonville Jaguars selected Monroe and Eben Britton with their first two picks in the 2009 NFL draft.

[12] During his time in Jacksonville, Monroe established himself as a cornerstone of the Jaguars offense, starting 62 of 65 games played and missing only 3 of 68 due to injury.

He had the highest base salary on the team and had been plagued by injury problems that caused him to miss 17 of 34 regular season and postseason games the previous two years.

[27] Monroe also disclosed that he had recently noticed signs of memory loss and planned to undergo a battery of tests to evaluate his current health status.

Monroe has pointed to the heavy use of addictive opioid drugs in the league and says players should not be punished for choosing a safer alternative that could help them better manage their pain.

[29] Monroe has also cited the neuroprotective properties of cannabis that could help treat and prevent the serious brain injuries and diseases that are well-documented among NFL players.

[31] Monroe has been joined by a number of retired NFL players who have attested to the medicinal benefits of cannabis and called on the league to change its stance, including Jim McMahon, Jake Plummer, Kyle Turley, Nate Jackson, Eben Britton, Leonard Marshall, and Marvin Washington.