The 38-year-old, the youngest member of Chancellor Angela Merkel's cabinet, shot to fame when he first joined the top ranks of government as federal health minister in 2009.
Now he is line to become the official number two to Merkel as her government's vice-chancellor, as long as his Free Democratic Party (FDP) confirms him as expected as its leader at a conference on Friday.
The FDP, the junior partner in the ruling coalition, chose Rösler on Tuesday to replace Rainer Brüderle as economy minister. Brüderle is to become his party's leader in parliament.
A heart and chest surgeon by training, Rösler was adopted as a nine-month-old baby by a German couple from an Vietnamese orphanage. His exact date of birth is unknown, though officially listed as February 24.
He was brought up by his adoptive father, a career military officer, after the couple split when he was just four.
A Westerwelle protege, Roesler last year steered a disputed set of health reforms through the German parliament that increased the financial burden on patients in an attempt to address healthcare deficits.
Rösler joined the FDP in 1992 and was elected to the Lower Saxony regional parliament in 2003.
Appointed state economy minister in early 2009, Merkel brought him into the federal government after winning a second term in September that year.
Once asked by Stern magazine if he was bullied at school because he was Asian, Rösler replied tongue-in-cheek that bullies steered well clear "because people always think all Asians are karate experts."