A Rhok charges a model and scores a critical on it, pitching the model. The model contacts another model of the same size.
Would the collateral damage roll be POW12 or POW14? Pitch says the POW of the weapon, and Gang is +2 to melee damage rolls, but I don’t believe melee damage rolls directly modify the POW of the weapon.
Here’s the important part of collateral damage rolls:
Here’s the critical part of Gang, emphasis mine:
Gang cannot apply because it gives a model +2 to melee damage rolls, but collateral damage does not come from an attack or model.
Also, to answer the question that wasn’t directly asked, but is nonetheless important:
Assuming the Rhok’s target was in melee with another model in the same unit, the Rhok’s attack roll will gain the +2 bonus from Gang. The throw movement is resolved in Step 7 of the timing chart (“Resolve all other effects triggered by hitting or missing.”), but damage is not resolved until Step 8.
If the charge target is thrown out of melee with other models in the unit, the Rhok will not get Gang’s +2 bonus to the damage roll, because Gang’s requirements are no longer met when the damage roll happens.
In each case, collateral damage is calculated normally: it depends upon the base size of the model suffering collateral damage compared to the Rhok’s base size.
Hope this helps! 