I've dug into this a bunch while trying to settle debates with friends, and the short-ish version is: there isn't a single unified Wii 'Naruto' roster—there are several Wii titles and each one has its own selectable cast. If you’re looking at the 'Clash of Ninja Revolution' trilogy on Wii (the most common reference), expect staples like Naruto Uzumaki, Sasuke Uchiha, Sakura Haruno, Kakashi Hatake, Rock Lee, Neji Hyuga, Shikamaru Nara, Gaara, Temari, Kankuro, Orochimaru, Jiraiya, Tsunade and a bunch of villains/late additions such as Itachi Uchiha, Pain (Nagato) and members of the Akatsuki across different installments.
From personal experience, the first Revolution game focuses more on the Konoha 3–5 and classic Chūnin Exam-era fighters, while Revolution 2 and Revolution 3 expand into later arcs and add unlockable characters and transformations. There are also support characters, alternate forms (like Sage Mode Naruto or Sasuke’s Mangekyō versions in later entries), and a handful of hidden unlocks you can get by completing arcade or story modes. If you tell me which Wii Naruto title you meant, I can list the full, precise roster for that game.