Roslagen is the name of the coastal areas of Uplandia in Sweden, which also constitutes the northern part of the Stockholm Archipelago. Historically it was the name of all the coastal areas of the Baltic Sea, including the eastern parts of lake Mälaren, belonging to Svealand. The name is derived from Roden, which is the coastal eqivalent to inland Hundreds. When the King would call to Leidang, the Viking Age equivalent to military conscript service, a Roden district was responsible for raising a number of ships for the leidang navy.
Etymologically Roden, or Roslagen, is the root of the Finnish and Estonian names for Sweden: Ruotsi and Rootsi. The background of Rus, as in Kievan Rus' or Russia, is the same as in the Finnish and Estonian usage and is believed to derive from Varangians, the Vikings from Roslagen.