I believe that the plural to “rolls” refers to the different magic items and different implements referred at the start of the sentence. I believe this because the first two paragraphs are all written with plurals. I bolded the plurals below.
Note that the sentence is referring to what each (singular) bonus applies to.
PH said:
For items that give an enhancement bonus, this entry specifies what that bonus applies to: AC, other defenses, or attack rolls and damage rolls.
Magic weapons and implements grant their enhancement bonus to attack rolls and damage rolls only when you use powers delivered through the weapon or the implement (or directly from the weapon or the implement, for items that have attack powers).
There's no distinction made as to which attack rolls should be affected and which should not - the text speaks of attack rolls in general. The text also points out that the power states if it is performed via a weapon or implement. The section on how to read a power (p. 54) and specifically the bit about keywords on the opposite page explain that the weapon/implement keywords "
identify items used with the power.", and mentions again that the enhancement bonus (and proficiency bonus, for a weapon) applies to attack rolls "
when you use a power that has the associated keyword". Note also that the concept of "base attack bonus" as explained on p. 274 is
per-power (which you should calculate for all powers including basic attacks) and includes "an enhancement bonus (usually from a magic weapon or implement)"! The attack roll in general is explained to consist simply of "the power's" base attack bonus, situational modifiers (combat advantage etc), and bonuses and penalties from powers affecting you.
It seems to me that you add the appropriate bonuses to all attack and damage rolls made by the power.
For (a confusing) example, the pit fighter's All Bets are Off would gain the full enhancement bonus to both primary and secondary attack and damage rolls. Weapon Focus applies to "damage rolls with your chosen weapon group", and counterintuitively could apply as well. Certainly, this is unfortunately, but the converse simply doesn't work. If you dont' let the enhancement bonus apply, then the secondary attack will eventually miss almost always, being up to +10 behind the primary attack(weapon prof. bonus, enh. bonus, fighter weapon specialization).
The rules are obviously simplified, but what would be the point of tracking separate attack bonuses just for such specific cases? The powers would simply become more complex to account for their own bonuses to compensate for the lack of a weapon bonus and the balance would be almost the same.
In short, the definitive sections to refer to are the "attack roll" section on p. 274 and the damage roll on p. 276. The section on magic items is simply summarizing the purpose of an enhancement bonus, and if you read it closely, you'll probably come to the same conclusion, but it's easier to just look to the definitions of attack roll and damage roll - which take into consideration the enhancement bonus of magic weapons.