Sheriff Jim Valenti is a main character of Roswell. At first a major antagonist, he later became an ally to the Pod Squad when he learned the truth. His relationship with the group was cemented after Max saved his son Kyle, after he was shot. Some time prior to the Pilot, his wife left him and their son Kyle. Jim Valenti and Amy DeLuca, Maria's mother, have an interesting history. 20 years prior to the pilot episode Jim, at the time a Deputy, arrested Amy DeLuca during a protest. During Season 1 the two begin dating, but this soon ends after Amy is afraid she is once again making a romantic mistake. Throughout the following seasons the two continue flirting, although never rekindle their relationship officially.
Valenti is shown as a major antagonist in the first season, albeit a sympathetic one. His father was also the sheriff of Roswell, and was ridiculed for his insistence that aliens live among humans. Valenti inherited from his father an old autopsy photograph from the 1950s of a body killed by inexplicable means, with a silver handprint on the chest. In the pilot episode, Valenti is called into the local restaurant, the Crashdown Café, where a shooting has occurred. Although no one was apparently injured, and the young waitress Liz Parker insists that the red mess on her uniform is ketchup, a pair of tourists insist they saw the girl get shot, and a young man ran up to her and did something to her before running off. There is also no bullet found in the café. Valenti notes the presence of empty bottles of Tabasco sauce on one of the tables, and later notices more in the Jeep of teenager Max Evans. Valenti becomes convinced that Max was in the Crashdown that day and that he somehow healed Liz. He steals Liz's waitress uniform, which has a bullet hole in it, and gives it to a friend of his in the FBI for analysis.
His son Kyle then tells him that he saw a silver handprint on Liz's stomach when they were on a date, similar to the one in the photograph, and Sheriff Valenti suspects that Max is not a teenager but rather a decades-old alien and a murderer. The FBI agent returns, telling him there was nothing found on the dress, and proceeds to remove any files on aliens from Valenti's office. Valenti is convinced, however, that the FBI is lying to him and conducting its own investigation. He continually investigates Max throughout the first season, but gradually becomes aware that, although he is an alien, Max is a good person. When Max is kidnapped by Agent Pierce and the Special Unit of the FBI, Liz comes to Valenti for help. He helps rescue Max from their stronghold and is let in on the secret: Max, his sister Isabel and their friend Michael Guerin are aliens that were raised as humans. Valenti then helps the group vanquish the Special Unit. When Kyle is shot and dying in the melee, Max heals him, and Valenti expresses his gratitude, promising to always be there for Max and the others.
Valenti is first helping the aliens by using his legal powers to cover up their actions. He also accepts Tess Harding into his house when Nasedo dies. While being investigated by the New Mexico State Board of Police, Valenti helps Isabel and Max find a buried girl in the woods, which jeopardizes his position as the Sheriff of Roswell. Agent Duff of the FBI, who is reviewing him, promises to help him get his job if he cooperates in telling the story of the crystals and gets his job back. It is unclear as to when he lost his job, because he was Sheriff, but at the beginning of season three, he isn't Sheriff anymore. He is also drawn into Maria's world as he dates her mother, Amy DeLuca, throughout the season without really going anywhere. It also reconciles Maria and Kyle as they often joke about it. Valenti also takes her to the prom as chaperones. He gets deeply hurt when Tess, who helped remind him about real family traditions, was revealed as Alex's killer. But he was happy that it had brought him back together with his son, Kyle.
When Kyle tell his father that he can't support the family alone, Jim goes and gets a job as lead singer in the band, Kit Shickers. He often at the party scenes because he's often asked to perform at them. He accepts giving Isabel away at her wedding, but doesn't follow through because her own father steps in. Often in the season, he and Kyle have to deal with their own problems. In the Christmas episode, "Samuel Rising," Kyle has to deal with the fact that Valenti shows interest in younger women. In the series finale episode "Graduation", Valenti gets Kyle a job at the Sheriff station. When Kyle rejects it, he also tells his father if he could get a job for his son, he could get one for himself. He becomes the Deputy Sheriff, which helps the "pod squad" because he can give false information to them.