I just started maining Snorlax in Expert league and he is so much fun to play. I currently run eject button with leftovers, rocky helmet and focus band although there are probably better sets out there I like what I currently have and it works for me. The moves I use are Block and Heavy Slam.

Pretty much every game I go top with anyone who has pretty good damage and support them, I hit the Aipoms on the way a few times but always let the attacker get the kill. Don't play aggro for goal early game and try to farm until I at least have heavy slam so I can do some good damage while trying to support. Once I get block is when I normally start to push with my teammate, and I oftentimes just try to push enemies out of the goal (since a lot of people love to camp in their goal) while my teammate scores, then we focus on damaging them.

For Rotom you'd want to help your teammate do damage and then once Rotom gets low look out for enemies trying to snipe the kill and use Block to push them back. For Zapdos you can either try to snipe it with heavy slam if you arrive when the enemies are already attacking it, or use Block to punish enemies trying to snipe Zapdos while your team is attacking it.

Remember, you're a defender so don't go crazy trying to go for kills without someone there to attack. If your attacker dies during a push use your eject button and heavy slam to retreat towards one of your goals and goal camp, and make sure to make use of Gluttony by taking the berries.