From a young age showed Jean -Julien Rojer talent for the sport of tennis. At the age of 14, he won the club championship by Racing Club Team Curacao and the National Championships of the Netherlands Antilles. He attended UCLA and was there with Marcin Matkowski the best double the ITA ( Intercollegiate Tennis Association). In 2002, he led the double ranking and was 35th in singles.
In the same year he turned professional and was especially at Future tournaments in use. Although he was able to win some Future tournaments in the next few years in an individual, he was more successful in doubles. But the breakthrough in the advanced world leaders he succeeded in 2008, when he found his Swedish doubles partner Johan Brunström. Together they won the some Challengerdoppelturniere and reached four ATP tournaments in 2009 in the final. Within 2 years, Rojer improved from rank 187 (end of 2007 ) ranked 43
In 2010 he succeeded with his new doubles partner Eric Butorac of the first tournament victory on the ATP Tour in Tokyo. In the same year they won the Stockholm another title. At the start of the 2011 season Rojer achieved the best performance in a Grand Slam tournament: the Australian Open, he reached the semi-finals with Butorac, where they lost to the eventual champions carrier Bob and Mike Bryan. During the season, the duo won three more tournaments in Estoril, Nice and Kuala Lumpur. Despite the common successes, Butorac and Rojer parted at the end of the season surprising; Butorac chose the Brazilian Bruno Soares as a new partner, while Rojer began the 2012 season with the Pakistanis Aisam -ul- Haq Qureshi ..
From 2012 Rojer plays for the Netherlands; the reason for this is that the National Olympic Committee of the Netherlands Antilles was dissolved and the players had to decide whether they want to compete for either Aruba or the Netherlands at the Olympic Games in 2012. Rojer opted for the Netherlands and therefore no longer occurs for Curacao in competitions at.
The new partnership was launched initially with little success because, although they reached the second round at the Australian Open, followed by a series of first- and second-round defeats. Only in the clay court season, won the duo to ride, they reached the semi-finals in Casablanca and Nice, before they could celebrate the first joint title in Estoril against Julian Knowle and David Marrero. In Roland Garros they reached even the semi-finals where they were eliminated against the Bryan brothers. The grass season they launched successfully winning the title in Halle. During the season they were able to record any further tournament victory, however, Rojer qualified for the first time in his career on the ATP World Tour Finals in London, where they have failed because in the preliminary round. At the Australian Open in 2013 Qureshi and Rojer failed in the second round, but they were able to record a great victory in March: the two won the final of the Miami Masters Mariusz Fyrstenberg and Marcin Matkowski against; Rojer for this was the first victory in a tournament of this high category.
Rojer occurred between 1998 and 2007 in respect of the Netherlands Antilles in the Davis Cup. In 31 matches, he won 28 of 34 singles and 14 double of 17 games. He was the most successful players on the team and at the same time record player. After the dissolution of the Antilles and the decision Rojers future to play for the Netherlands, he was called into the squad for the first time the Dutch Davis Cup team in the 2012 season.