Cognomen Rosmarus (Mursu 
, Rosmarus) , in all the world, is a rare family name. The cognomen Rosmarus is habitual in Northern Europe, particularly Finland, where it is quite a rare surname, Sweden, where it is a rare surname, and Estonia. Not in comparison with a country's population, this name is the most popular in Finland, the United States, and India. Much less frequently, Rosmarus is the forename as well as the last name.