From German-Polish origins, he came to Serbia as an assistant professor and never left, among his many contributions is the introduction of Aseptic practice into the operating room and the surgical treatment of hernia in conscripts.

[1] Sondermajer was born in Czernowitz, capital of the Duchy of Bukovina, Austrian Empire (present-day Chernivtsi in Ukraine), a son of Franciszek Sondermeier, native of Bavaria, and a Polish mother.

He finished high school in Lviv and received his medical degree in 1884, from the Polish Jagiellonian University in Kraków, specializing in surgery.

He was immediately assigned to the Army Medical Service with the rank of captain,[3] his first duty was to set up a Surgical Department at Belgrade Military Hospital.

[5] The Ottoman army was decisively defeated by the coalition but a month later the Second Balkan War started when Bulgaria turned against its two former allies in a surprise attack.

[10] The number of physicians and para-medical staff that Serbia had at the beginning of the war was not sufficient; the Medical Corps was inadequately and insufficiently equipped; there was no causal treatment since this was the pre-antibiotic era, and there was a general weakness of the entire population, which also contributed to the mass morbidity and mortality.

[11] The decision was made to ask officially, through embassies in Great Britain, France, and Russia, for immediate help in the form of 100 physicians to suppress the epidemic.

[12] In October 1915  Austro-Hungarian, Bulgarian and German forces launched a new offensive, the Serbs continued fierce resistance and gradually withdrew.

On 25 November, the Serbian High Command issued the order to retreat through Montenegro and Albania, to join the Allies and continue the war out of the country.

[13] The Serbian High Command emphasised that its army was not in a favorable condition for a counteroffensive, but that capitulation was viewed as a worse choice.

Dr. Sondermajer and his two sons crossed the snowy Albanian mountains in the arduous winter retreat with the rest of the Serbian army, with no food and medical supplies.

Dr. Roman Sondermajer married Stanislava Durić, daughter of Minister of Defence General Dimitrije Đurić, and granddaughter of Minister of Education Dimitrije Matić, Stanislava Sondermajer was a member of the Circle of Serbian Sisters, a humane society of volunteer nurses, following the Austro-Hungarian attack on Serbia, the Circle of Serbian Sisters relocated from Belgrade to the wartime capital Niš, where its members worked in the town's hospital, collecting money and clothes for the wounded.