Rosnan was in love with a woman named Alyss, who, despite her ugly apperance, was well loved and sought after because of her beautiful golden hair. Because of his own uglyness, Rosnan never pursued Alyss, fearing that she would never have him.
One day, a Topaz dragon abducted Alyss so it could use her hair to line its nest in the Os-Mine Hills. Rosnan chased after the dragon and battled it to win her freedom, but he was no match for the dragon and nearly lost his life. Alyss, watching Rosnan's bravery, cut her hair off with his sword and offered it to the dragon in exchange for his life, to which the dragon agreed.
Confronted with the sight of her own uglyness, Alyss ran deep underground, with Rosnan following close behind her. He eventually caught up to her on the hidden island of Keras, where he proclaimed his love for her even without her golden hair. Alyss accepting his love, and the two were allowed to live on the island with its people, the Kerons.
Lief and Jasmine both seperately read the tale of The Girl with the Golden Hair in the Deltora Annals, which allowed them to decipher the location of the Pirran sea.
When Lief, Barda, and Jasmine arrived on Keran, the Kerons explained that Rosnan and Alyss' children married Kerons, and so most modern Kerons have some Deltoran blood in them. Emlis, the son of the piper Tirral, even has golden hair like Alyss.
Rosnan was described as being ugly, and as plain looking as Alyss.