I have to say, I am not enthralled with the "roles" idea. It assumes too many things about a group's playstyle. For instance, where's the "social skills" role? Lots of groups play a political intrigue style, but I don't see any "Fast Talker" classes. Some groups also prefer the "leading an expedition" feel, with hired muscle, guides, etc. Are the "Leaders" going to be useful for leading groups of any size - like hired men-at-arms? If no, it may feel gamist and arbitrary; if yes, they may be too powerful balanced against the assumed 5-member group...
It's probably not a bad idea to have advice like "This is what this class is good at; this is the style they are best suited for." etc. But i'd prefer two things:
1. That "basic and necessary" skills are spread around a large-ish number of classes, so that no one class is necessary. Monte's AU did this by making healing magic, arcane magic and certain key skills (i.e., Open Lock/Disable Device) more widely available. Certain classes were much better at them, but a party that lacked both Greenbond and Greenwitch was not without healing magic. Only the "pure martial" classes were without healing magic entirely.
2. That each class has it's own role. I want Core classes that are unique and interesting choices, not just different flavors of "Defender" and "Controller."
Of the two points, I think 4e will do a decent job of delivering on #2 - it's point #1 I'm more worried about.