Family name Rousen (Русен 
, Rousen 
, Reuser 
) , globally, is a rare cognomen. The cognomen Rousen is characteristic of Netherlands, where it is quite a rare surname, Bulgaria, and Canada, where it is a very rare surname. Measured by absolute frequency, this name is the most popular in Netherlands, Bulgaria, and the United States. Very seldom, Rousen is the forename as well as the last name.