"Roon" was transferred to the Baltic in April 1915 and participated in a series of offensive operations against Russian forces, including the attack on Libau in May, the Battle of the Åland Islands in July, and the Battle of the Gulf of Riga in August. The threat of British submarines led to her decommissioning in 1916, after which she was employed as a training ship and an accommodation vessel. Plans to convert her into a seaplane tender late in the war came to nothing owing to Germany's defeat in 1918, and she was stricken from the naval register in 1920 and broken up the following year.