At age 19, Robert joined what is now Team Visma | Lease a Bike. In 2006, he was part of Rabobank Contintental Team, which at the time was the benchmark for developing young riders into pro riders. He impressed with a second-place finish in the Tour de l’Avenir, and a year later—quite exceptional for that time—he made the leap to the professional ranks of what was then the only professional cycling team in the Netherlands.

The Varsseveld native brought with him a strong resume, and the expectations in Dutch cycling, which had not played a significant role in the general classifications of the Grand Tours for many years, were immediately high. Robert met these expectations as a 20-year-old by riding very consistently and winning a stage in the Ardennes during the Tour of Belgium in his first professional year.

A year later, he continued in that vein, finishing in the top ten in the general classifications of the Tour of California, Paris-Nice, and the Dauphiné. He also started his first Grand Tour that year, finishing seventh in the Vuelta a España.

In 2009, he improved by one place in the final classification in Spain after being forced to withdraw from the Tour de France earlier that season due to a broken wrist. Additionally, he claimed his first of two victories in the Giro dell'Emilia.

In 2010, Robert prepared for his second Tour de France, which started in Rotterdam that year. In the lead-up to the race, he racked up top-ten finishes in the general classifications of Tirreno-Adriatico, the Tour of the Basque Country, and the Tour de Suisse, where he also won a stage. Despite some bad luck, he became the first Dutch rider since 2001 to finish in the top ten in the Tour.

In 2011, Robert again aimed for a top finish in the Tour de France. His build-up to the Tour was highly successful, with a victory in the Tour of Oman, a second place in Tirreno-Adriatico, and a third in the Tour of the Basque Country. However, lingering effects of a crash hampered his Tour performance, and he was unable to match his result from the previous year.

In the fall of 2011, Robert suffered a broken femur, which required a full winter of recovery. This affected his preparation for the 2012 Tour de France, which he again targeted. Despite the setback, he won the Tour of California in May and once again finished in the top ten in the Tour de Suisse. Unfortunately, he crashed during the Tour itself and had to abandon the race. He then shifted his focus to the Vuelta, where he finished sixth in the overall classification.

In 2013, the team continued as Blanco Pro Cycling, later becoming Belkin Pro Cycling. That year, Robert chose to focus on the Giro d’Italia for the first time in his career. However, he had to withdraw in the final week due to illness. He then rode the Tour de France in a supporting role for Bauke Mollema and Laurens ten Dam, both of whom spent a significant amount of time in the top ten of the general classification. In the fall, Robert achieved an impressive victory in the GP Quebec.

2014 was a strange year in Robert's career. He struggled with heart rhythm issues and underwent surgery. He returned to competition and was once again able to compete with the best riders for a top-ten finish in his beloved Vuelta a España. However, due to family circumstances, he had to leave the race in the final week.

After dealing with heart problems and other unfortunate events in his life, Robert was determined to make a comeback in 2015. Following a mixed early season, he once again targeted the Tour de France. For three weeks, he climbed with the best riders, finishing sixth and as the best Dutch rider in the general classification, representing the team that had by then become known as Team LottoNL-Jumbo.

Motivated by that strong performance in the Tour, Robert set his sights on the overall classification in the 2016 Tour de France. However, a crash in the Tour de Suisse prevented him from starting. He then shifted his focus to the Vuelta, where he aimed for a stage win instead of the overall classification. He succeeded, winning a mountain stage to the Aubisque after a long breakaway—his first stage win in a Grand Tour.

Buoyed by that stage win, Robert decided to focus more on winning stages rather than overall classifications from then on. By this point, he had become one of the most experienced riders in a team that was rapidly evolving, and he was still a key part of it. With his focus on stage wins, Robert returned to the Tour de France. A day after narrowly missing out on a stage win, he had to withdraw due to a crash.

As an experienced rider with a strong palmarès, Robert was given the freedom to pursue stage wins again in 2018. At the same time, the team continued to develop, and he proved to be highly valuable in a supporting role for George Bennett in the Giro and Primoz Roglic and Steven Kruijswijk in the Tour.

In 2019, Robert had a stroke of bad luck in the spring when he broke his pelvis in Liège-Bastogne-Liège. He shifted his focus from the Giro to the Vuelta, where he helped Primoz Roglic to the team’s first Grand Tour victory, by then known as Jumbo-Visma.

In the COVID-affected year of 2020, Robert once again rode two Grand Tours in support of leader Primoz Roglic. The Slovenian narrowly missed out on winning the Tour, but he did secure another Vuelta victory. Robert played an important supporting role in both races.

By now, the role of road captain suited Robert perfectly, given all his experience. The team once again aimed for the Tour victory with Robert as a key helper. Unfortunately, he crashed out in the third stage. He then helped Primoz Roglic to a third consecutive Vuelta victory.

The Vuelta became more and more Robert’s race. In 2022, after winning the team time trial in Utrecht, he took the red leader's jersey. However, Roglic, the team leader, was unable to secure his fourth consecutive Vuelta victory due to a crash.

In 2023, Robert was once again present in Spain as Jumbo-Visma achieved a unique treble, winning all three Grand Tours in a single year and occupying the entire podium in Madrid with Sepp Kuss, Jonas Vingegaard, and Primoz Roglic.

2024 marks the final year of a remarkable cycling career. Thirteen professional victories, dozens of top-ten finishes in WorldTour classics, stage races, and Grand Tours, and an untold number of kilometers at the front of the peloton. A rider who joined the pros as a top talent, fulfilled expectations by climbing with the best in the Tour de France, successfully sought stage victories, and played a crucial role as an experienced road captain in the final years of his career.