Ozroar is the name that has been given to the monarch who was the grandfather of Ozma and the father and predecessor of Pastoria.
Ozroar is not a creation of the Royal Historians of the "Famous Forty" Oz books; rather, he is found in later Oz literature and fan fiction. He is sometimes though not always called the first king of Oz, though this contradicts the details in L. Frank Baum's original works — in Dorothy and the Wizard in Oz Baum suggests a long line of earlier monarchs.
Ozroar first appears in Henry Blossom's The Blue Emperor of Oz. He recurs in later works, including The Forest Monster of Oz by Chris Dulabone and Robert Evans, and Prince Pompadore in Oz by Nathan DeHoff. (Author Blossom made Ozroar the brother of King Pompus of Pumperdink as well as Ozma's grandfather.)
In The Magic Book of Oz, Scott Dickerson creates a different figure, Oz Bozkinz, as Pastoria's father and Ozma's grandfather.
In Paradox in Oz, Edward Einhorn introduces King Oz, Ozma's grandfather, who serves as antagonist and ally at different parts of the novel. Pastoria is not mentioned.