Marotti began his coaching career as a graduate assistant at Ohio State, where he first coached with Urban Meyer. After two seasons, he took a full-time position at West Virginia, where he spent two years as a strength assistant. Marotti then left for Cincinnati, where he spent seven season leading the Bearcats strength and conditioning.
He once again left Ohio, this time for South Bend, Indiana, when he became the director of strength and conditioning at Notre Dame in 1998. Marotti was reunited with Meyer during this stint. In 2005, when Meyer took over as head coach for Florida Marotti joined Meyer's coaching staff as director of strength and conditioning. At this time, The Gators found success and won two national championships and three SEC championships. Following Meyer's short retirement following the 2010 season, he stayed on with Will Muschamp for one season.
When Urban Meyer took over at Ohio State, Marotti returned to Ohio, where he was named assistant athletic director for football sports performance. Since then he has won another national title and three Big Ten titles. Following Meyer's second retirement in 2018, he remained part of the Ohio State coaching staff under Ryan Day.