He first appears in written sources as a witness to the Pact of Vilnius of January 1401. His patrimony was in Deltuva, but he also had possessions in Samogitia and volost of Svislach. In 1409, he became Elder of Samogitia and instigated the Second Samogitian Uprising on orders of Vytautas, Grand Duke of Lithuania. The uprising grew into the Polish–Lithuanian–Teutonic War and it is believed that Rumbaudas commanded Samogitian troops in the Battle of Grunwald (1410). After the war, he became Grand Marshal of Lithuania while his brother Mykolas Kęsgaila became Elder of Samogitia. In 1413, he was among Lithuanian nobles negotiating the status of Samogitia with Benedict Makrai, a mediator appointed by Sigismund of Luxemburg. In 1422, he witnessed the Treaty of Melno. In 1422/1423 he is mentioned as Elder of Vitebsk. In 1429–1430, he was sent to Poland to negotiate coronation of Vytautas as King of Lithuania.