Jim Valenti is a central character in all three seasons of Roswell, and possibly the one person who changes the most over the course of the show. At first, he’s the primary authority figure that the kids are trying to keep from finding out the secret.
Over the first season, they start to get hints that Sheriff Valenti is more sympathetic to them than he seemed and that he might become an ally. He saves Max from Everett Hubble in the episode “The Convention”, and returns an alien orb to them in “Tess, Lies and Videotape.” At the end of season one, in “The White Room”, Liz comes to Jim to ask for his help saving Max from the Special Unit, and he does, even pretending to betray the kids to Agent Pierce in order to lure Pierce into a trap. Jim’s friendship with Max is sealed when Max saves Kyle’s life in “Destiny.”
In season two, Valenti’s instincts to protect and help the alien kids eventually cost him his position as Sheriff, and he struggles for most of the rest of the series to find a new job and new identity, including ventures into woodworking, country music, and private security. At the end of the series, he finally chooses to return to county law enforcement, becoming a deputy under the new Sheriff, and his last choice is to help Max and his friends leave town safely.