The only Poke you have that can beat Roobushin is SR weak and choiced, that's something you should probably look into.
Snorlax should probably get Leftovers with Body Slam > Giga Impact. Excadrill needs Life Orb > Focus Band. Lastly I'd use Thunderbolt > Dark Pulse on Rotom for another option if you don't want to volt switch out. Besides, Shadow Ball hits everything for supper effective that Dark Pulse does.
Good luck with your team. :D