Roshi changes currently existing barrier (similar to tendo), so he deletes all the profit either team could gain from it. If it's your barrier, you lose bonuses. If it's enemy barrier- enemy loses bonuses from it.

I have a little follow up question for this, consider having Gara Kazekage in team. But was wondering if Roshi attack will benefit from barrier when he launches it or the duff will be cancelled at the moment Roshi cast his mystery?