Rockenfeller began karting in 1995 at the age of eleven, winning the Bambini North state championship and competing in regional and national karting through the 1990s. In 2001, he moved to cars and finished fourth in the Formula König championship. He joined the Porsche Junior team in 2002, racing in the German Carrera Cup and partial Porsche Supercup. By 2003, he had reached the international stage with an American Le Mans Series debut at Petit Le Mans.
His Porsche factory career peaked in 2005. He won the German Carrera Cup in 2004 and earned full factory status the following year, taking the GT2 class driver championship in the FIA GT Championship alongside Marc Lieb for GruppeM Racing with six class wins including the Spa 24 Hours. That same year, he won the GT2 class at the 24 Hours of Le Mans with Lieb and Leo Hindrey. In 2006, he won races in the American Le Mans Series and Grand-Am before making the move to the Deutsche Tourenwagen Masters.
Rockenfeller became an Audi factory driver for 2007, racing an A4 DTM for Audi Sport Team Rosberg in the Deutsche Tourenwagen Masters. He simultaneously continued his Le Mans Prototype commitments, driving for Audi Sport Team Joest in the Le Mans Series in 2008 alongside Alexandre Prémat. Despite not winning outright, the pair claimed the LMP1 title at the 1000 km of Silverstone after a Peugeot retirement. He remained with Team Rosberg in DTM for 2009 before beginning his most significant season.
In 2010, Rockenfeller opened the racing calendar by winning the Rolex 24 at Daytona overall with Action Express Racing, co-driving alongside João Barbosa, Terry Borcheller, and Ryan Dalziel. Later that year, he stood on the top step of the Le Mans podium, winning the 24 Hours of Le Mans overall with Audi, adding the most prestigious endurance prize to his growing collection.
The 2011 Le Mans was overshadowed by a serious accident. Shortly after nightfall, Rockenfeller was involved in a violent crash at the kinks between Mulsanne Corner and Indianapolis following near contact with the number 71 car. He climbed from his car and jumped to safety over the Armco barrier, sustaining only a minor flesh wound and spending one night in hospital for observation.
The high point of his DTM career came in 2013, when Rockenfeller won the championship driving for Audi Sport Team Phoenix. It was Audi's answer to Mercedes domination of the preceding years and placed Rockenfeller among the DTM's title-holders. He competed in DTM through the 2021 season, his final campaign, finishing eighth in the points with podiums at Lausitzring, Circuit Zolder, the Nürburgring, and the Hockenheimring for Abt Sportsline. He departed from both DTM and Audi at the end of that year.
After departing Audi, Rockenfeller explored new categories. In 2022, he made two starts in the NASCAR Cup Series for Spire Motorsports in the No. 77 Chevrolet, finishing 30th at Watkins Glen and 29th at the Charlotte Roval. He was subsequently part of the celebrated Garage 56 entry at the 2023 24 Hours of Le Mans alongside seven-time NASCAR champion Jimmie Johnson and 2009 Formula One world champion Jenson Button, driving the Next Gen Camaro prepared by Hendrick Motorsports. He also made further NASCAR Cup Series appearances in 2023, driving for Legacy Motor Club.
In IMSA, Rockenfeller joined JDC-Miller MotorSports in 2023 for their GTP programme, driving alongside Tijmen van der Helm.
Rockenfeller's career honours span three decades and four major categories. His principal achievements include the FIA GT Championship GT2 title in 2005, the Le Mans Series LMP1 championship in 2008, the 24 Hours of Daytona overall victory in 2010, the 24 Hours of Le Mans overall victory in 2010, the 24 Hours Nürburgring overall win in 2006, and the Deutsche Tourenwagen Masters championship in 2013. Few drivers in motorsport history can match his breadth of achievement across sports car racing and touring car competition at the factory level.