According to Chris Tom, handler of Player Relations & Communications, the new roster will help get newbies accustomed to the ins and outs of League. "Our goal is to improve the way players learn to play League of Legends when they're first starting out," he writes in the patch notes. "These champions were picked because of how easy they can be learned and how enjoyable most new players find them."
Unfortunately, neither Tom nor Riot revealed which champions will be part of the static roster. That being said, it's not completely outside of reason to speculate that the selection would include champions with the "Recommended" attribute. For those unfamiliar with League, those champions are Garen (a knight), Katarina (an assassin), Nunu (a kid riding a yeti), Ryze (a sorcerer), Sona (a magic musician), Soraka (a divine healer), Taric (another knight), Tristana (a steampunk cannoneer) and Warwick (a werewolf).