Even if Genesect doens't get the SpA boost, standard Rotom is taking 68,5% - 81,32% from a LO bug buzz. This means that you can burn it, but that won't prevent Gene from killing your Rotom next turn and quite possibly take out other 1-2 Pokemon, until LO+burn damage consume its HP.
<ginganinja> can I add Pocket
<ginganinja> to his own blacklist
Join this group
if you're interested into joining Team Italy for the next World Cup of Pokémon.