Born November 22, 1897 in Kaufbeuren, Bavaria, was the son of a Bavarian forestry official and was educated in Augsburg.
During World War I, served in the German Army. After the war, began working as a journalist, serving for a time as a reporter in Augsburg and then as a literary critic in Berlin. Was friendly with members of the literary and artistic circles within Germany. Many of these friends were censored and targeted by the evolving Nazi power regime and were forced to flee the country for their lives.
Angry about the treatment of his friends as well as the emerging dictatorial regime in place, Roessler became a vehement opponent to the Nazi Party and to Adolph Hitler.
Roessler insulated his sources from the Allied Forces, such that no one but he knew their true identities. One of his contacts, to whom he passed information, was Xavier Schneiper, a proponent of Marxism who despised the Nazis. Schneiper passed information obtained from Roessler to a Swiss underground intelligence operation known as Bureau Ha. In 1939, Roessler warned Schneiper of Hitler’s intentions to invade Poland. He later provided Bureau Ha with explicit information detailing the Nazi’s planned invasions of France, Belgium and Holland as well as Nazi intentions towards Switzerland.
Sent information through Sandor Rado’s “Lucy” spy network (Lucy was Roessler’s codename) providing specific times, dates and locations of a German invasion of Russia. This information was the presented to Soviet intelligence but Josef Stalin refused to believe it and ignored it. Eventually, the Russians began to trust and rely on his information as it provided assessments of German troop strength and well as their plans for specific military activities. Many of these reports were delivered by Roessler mere hours after they were conceived and thus received by the Allies days, if not weeks before they were to be implemented. He further informed the Russians about what intelligence the Germans had about the Russian Army and its strategies.
Germany deduced that information was being passed to the Allies by persons located in neutral Switzerland thus and complained to the Swiss. In an effort to placate the Nazis) and therefore lessen the chances of a German invasion of Switzerland), the Swiss government arrested a large number of the Lucy network spies, including Roessler in May 1944 (in doing so, the government may have, in effect, saved the lives of these spies rather than having the Nazis deal with them).
Having financial difficulties in the post-War 1950’s, Roessler was believed to have sold innocuous information about Allied occupation forces and he was again arrested for espionage. Found guilty, he was confined to prison for one year. He would return to his publishing company and lives out his life, impoverished, in Switzerland until his death in 1958.