What is the point in a rotation system when the team has no real set style or understanding yet?
Simple, the set style is worked upon in training drillls and scrimmage sessions, theoretically every player in the squad should be well versed in the style we want to play and how that corresponds to their position(s) so that if called upon they can come in and do the job we want from them. What will separate the routine "starters" from the role players is their ability to continually make the right decisions during games, provide an extra bit of spark or creativity, read the game better and have better chemistry with their fellow "starters".
In short every player within the squad should know the basic fundamentals required of them to play their position(s) in the style Kenny wants us to play. This doesn't mean we should expect Skrtel to know how to play upfront in our system, but we should be able to expect him to know and to execute if deployed at right back for example, at least at the basic level the position requires in our system. No one expects him to bomb up the wings like Johnson or Kelly, that's why they're preferred there to Skrtel.
Another example is Lucas, he's our primary defensive/holding midfielder, but we should expect him to be able to perform well fundamentally as a more attacking midfielder should the need arise. Sure he might not do it as well as Gerrard would, especially if the role was entirely attacking, but he should be able to fill in there if he's a better option than (insert name here) and someone else we're grooming for that position can't play for whatever reason.
That being said I think Kenny is a fan of rotation to be honest, in fact it would seem the only people that aren't fans of the policy are members of the media, people who have a personal vendetta against Rafa Benitez, or both.