Is there any PROOF that each class is going to be one power-source + one role?
It is very possible that certain roles are best suited to certain power sources, so there will be no obvious PS+R combo. Arcane Defender seems completely odd, as does Martial Controller. I'm sure we all can think of some manner of class that does just that, but I think those will be in future PHBs.
So how will the PH balance then? I'm thinking more by role than power source.
There are 8 classes* and 4 roles, two classes per role so that no class is required for balanced roles.
Defender: Fighter is the baseline (using all manner of weapon maneuvers) and Paladin will be the Alternate (mixing divine powers like smite with tanking abilities like knights challenge).
Leader: Cleric rules here with divine power for buffs and healing, but warlord will be the alternate using inspiration and tactics to achieve similar results.
Striker: Rogue is again baseline (thanks to sneak attack and urban skills) but the ranger will be just as good (using wilderness skills and skirmish).
Controller: Things get tricky here. We know the wizard is the archtypical controller, but what else fills that role? The warlock seems able to (from the playtest report) and does the sorcerer and druid. Despite this, I'm going to go with Warlock as the second controller, where the wizard will use classic spells mostly, the warlock will focus on a smaller pool of at will abilities. Plus, it just is asking for it with tieflings being in the mix.
Final Tally, we have...
Cleric (Leader, Divine)
Fighter (Defender, Martial)
Paladin (Defender, Divine)
Ranger (Striker, Martial)
Rogue (Striker, Martial)
Warlock (Controller, Arcane)
Warlord (Leader, Martial)
Wizard (Controller, Arcane)
Four martials, four "casters" (two arcane, two divine). Seems a good mix IMHO.