Roy apparently was one of the last ones cut, alongside Mewtwo. Both Roy and Mewtwo have victory theme listings, while no one else has. Mewtwo, in addition, also had a Classic Mode victory screen listing, which means that he went even further than Roy.
Early during development, when Sakurai answered questions from Japanese fans, Sakurai talked about the idea of giving personal victory themes to some characters. He also showcased Metaknight's as an example. When the development advanced, Sakurai dropped the personal victory theme idea, leaving only one to Metaknight, probably because it had been revealed already. So, Mewtwo and Roy likely made it at least to this phase where he was still planning to add personal themes.