In 1943 De Roos had started working for the Mees & Zn back in Rotterdam, where he soon became head of the Economic Bureau.
He became more generally known as member Social-Economic Council since early 1950s, and as author of articles in the Economisch-Statistische Berichten[REF] He was also editor for De Economist, member of the Royal Netherlands Academy of Arts and Sciences since 1980,[REF] and board member at the De Nederlandsche Bank [REF].