He was licensed as a merchant of the Danish Gold Coast and returned to Africa on board the ship Wilhelmine Galej in 1746.

The latter contains a foreword by the theologian Erik Pontoppidan in which he claims that black slavery is not incompatible with Christian commandments.

Römer did, however, have good local sources and the books contain valuable information about the history of the Asante (Ashanti) people and state.

The historian Ivor Wilks has described his works as "one of the best sources of insight into the nature of coastal Ghanaian society in the eighteenth Century".

On 2 June 1751, Rømer married Anna Cathrine Wedderkamp (c. 1732 - 5 March 1770) in St. Nicolas' Church in Copenhagen.