So.....I was playing B2
battled N's Zekrom using my Genesect, which holds a Rocky Helmet
the Zekrom used Zen Headbutt and Fusion Bolt, neither activates Rocky Helmet. The only thing I can think of, is that Teravolt (along with Turboblaze and Mold Breaker) negates it.
Won't be the first time an ability negates the activation of a hold item, Sheer Force did it with Red Card and Eject Button.