|Died||9 May 1521|
Roisersis was born into a military family in Jatxesusna, in western Namija, and studied in that city's Academy of Exploration. He subsequently accompanied Namijan merchants on expeditions to Txekrikar.
In 1520 he was financed by the crown of Namija to lead an expedition to Andamonia, to reestablish trade links with the cities of Tepec and Alacuaha, which had been Namijan dependencies in the early fifteenth century. The Roisersis expedition was one of the first major Namijan expeditions to Andamonia since the 1440s, and was the first to be extensively armed with gunpowder weapons including cannon. Arriving in Tepec, his company was well-received and spent a month residing in the city. On his departure, he was given guides by the prince of Tepec, and he led one hundred men south along the coast towards Alacuaha. He was refused permission to traverse the lands of the prince of Teraxi Yú, however, because of his alliance with Tepec. Roisersis' Tepeci guides led him inland before, hoping to manipulate Roisersis into fighting and defeating their rival, cutting southeast to bring him once more into the territory of Teraxi Yú. Within a day, his party was ambushed at Teraha and massacred; only twelve men survived to flee to Tepec.
The loss of Roisersis' company was a severe blow to Namijan prestige, and they sent further expeditions to recoup their losses and punish Teraxi Yú. Teraxi Yú, meanwhile, seized on the advanced Namijan weapons to assert its independence from the Andamonian emperor. The subsequent period of civil war saw the northern city-states purchase and steal firearms from Namija until, with Txekri assistance, the emperor restored his authority in the north. Sporadic conflict between Andamonia and Namija persisted for the next century or so.