Robertha spent the previous two seasons with PFC Levski Sofia in the Bulgarian first division after joining the club from SC Cambuur-Leeuwarden in the Dutch second division on July 24, 2019. The forward has scored 20 goals and recorded eight assists in 39 appearances across all competitions for PFC Levski Sofia. He scored his first goal for the club on his debut in the 2-0 win against Tsarsko Selo Sofia on Aug. 5, 2019.
Before joining PFC Levski Sofia, Robertha was with SC Cambuur-Leeuwarden in the Dutch second division after his transfer from Feyenoord on July 5, 2017. In two seasons with the club, Robertha scored 16 goals and recorded eight assists in 59 appearances. He scored his first goal for the club in the 5-1 win against Helmond Sport on Sept. 19, 2017.
Robertha is a product of the famed Feyenoord Academy in the Netherlands that has produced players like Robin Van Persie, Nathan Ake, and Anwar El Ghazi. After joining the academy at age 11, Robertha went on to appear in 63 matches for the U-19 and U-21 teams at the club. He scored 19 goals and recorded two assists during his time with the club. The 23-year-old appeared once for the first team at Feyenoord; making his debut as a substitute in the 1-0 win against Willem II Tilburg on May 1, 2016 in league play.
During his youth career, Robertha represented the Netherlands Youth National Team after growing up in Dordrecht. The forward scored three goals in 22 appearances for the youth national team at the U-15, U-16, U-17, and U-18 levels.