I have been brewing up a character build that uses Toppling Spell to knock creatures prone with Magic Missile. I stumbled across Kobold Style, specifically Kobold Groundling, and realized that if I could reliably trip with Magic Missile, I could apply Sneak Attack damage to prone enemies. However, I seen many posts online stating that you cannot apply sneak attack damage via Magic Missile because it does not make an attack roll.

A rogue's sneak attack text (from D20PFSRD):

Sneak Attack

If a rogue can catch an opponent when he is unable to defend himself effectively from her attack, she can strike a vital spot for extra damage.

The rogue's attack deals extra damage anytime her target would be denied a Dexterity bonus to AC (whether the target actually has a Dexterity bonus or not), or when the rogue flanks her target. This extra damage is 1d6 at 1st level, and increases by 1d6 every two rogue levels thereafter. Should the rogue score a critical hit with a sneak attack, this extra damage is not multiplied. Ranged attacks can count as sneak attacks only if the target is within 30 feet.

With a weapon that deals nonlethal damage (like a sap, whip, or an unarmed strike), a rogue can make a sneak attack that deals nonlethal damage instead of lethal damage. She cannot use a weapon that deals lethal damage to deal nonlethal damage in a sneak attack, not even with the usual –4 penalty.

The rogue must be able to see the target well enough to pick out a vital spot and must be able to reach such a spot. A rogue cannot sneak attack while striking a creature with concealment.

Casting Magic Missile against an enemy is, grammatically speaking, attacking an enemy, and the specific wording doesn't specify making an attack roll. Can someone please point me to where this distinction is made?