Roger of Conté was a Duke of Tortall. He is the only nephew of King Roald through an unknown sibling, and was heir presumptive of Jonathan of Conté at the time of his death.
History
Roger is brought to court by his uncle, King Roald, who wants him to teach the gifted pages sorcery and to try to find out who sent the Sweating Sickness that attacked the city. However, what Roald does not know is that Roger was the one who sent the disease in order to kill his cousin, Jonathan, as part of his plot to gain the throne of Tortall. Over the course of the following years, Roger makes further attempts to kill his cousin without arousing anyone's suspicion, including sending Jonathan to the Black City to face the Ysandir, and during the war with Tusaine in the Drell River Valley. He also attempts to kill Alanna of Trebond, known still as Squire Alan, multiple times because he is afraid that Alan/Alanna will interfere with his plot.
Roger has a few major accomplices in his plot for the Tortallan throne, notably Alexander of Tirragen, his former squire, and Delia of Eldorne, his implied lover. He cast a spell to prevent key members of the court, Sir Myles of Olau, Sir Gareth of Naxen, the Lord Provost, as well as Alanna, Jonathan and King Roald from realizing what he was doing or from acting on any of their suspicions. Alanna weakened the spell during her Ordeal of Knighthood enough that she could break free and reveal Roger's true intentions to the world. Roger challenges her to a trial by combat, in which he uses illegal magic in an attempt to beat her and also accidentally discovers and reveals her true gender, but Alanna manages to defeat him anyway.
While it was believed that Roger died from this duel, he did not. Instead, he was in a state called Sorcerer's Sleep, which allowed him to plan his revenge carefully. In the meantime, Delia managed to goad Thom of Trebond into bringing Roger back to life. King Roald, ever the peacemaker, returned all of Roger's estates and titles to him before his own death. On the day of Jonathan's coronation, Roger and his supporters mounted a full-scale attack. While most of his fighters believed they were attempting to put Roger on the throne, Roger's true plan was to destroy Tortall with a giant earthquake, presumably because he had been driven mad by his time in the Sorcerer's Sleep. However, Alanna managed to permanently kill Roger before his plan could come to fruition.
Magic
Roger's magical standing was never stated explicitly in any of the books, it is believed that he is the equivalent of a black robe mage from the university in Carthak, like Numair Salmalín and it was also said that Duke Roger was the most powerful sorcerer in the Eastern Lands. Gary of Naxen stated that "[e]very sorcerer in the Eastern Lands would think twice before taking him on." Furthermore, he was able to send the Sweating Sickness to Tortall while he was in Carthak, which was at least a month's worth of travel away.
Roger gets his magical gift from the non-Conté side of his family, and so the color of his magic is orange, rather than blue like Jonathan's. When Thom raised Roger from his grave, the spell leaves the two of them magically tied, and the color of each of their gifts changes to a dark blood red, a combination of Roger's orange gift and Thom's violet gift. Also, somehow this magical tie makes it appear that Roger has no magic at all.
Appearance
Roger is generally considered very attractive. He is over six feet in height, with fair skin, blue eyes, brown-black hair and a neatly trimmed beard. He is broad-shouldered and muscular, with strong-looking hands, and exudes charm and confidence. Before his first "death" he dressed very well and was vain of his appearance. After his return, his hair was too long and there were foodstains on his robe.
Trivia
In the original adult version of Song of the Lioness, Roger's character was bisexual and involved with Thom, as well as Delia of Eldorne. Furthermore, he hit on Alanna when he believed her to be Alan, who rejected his advances.