I shall fix this.https://replay.pokemonshowdown.com/gen7randombattle-771605327
If you check the turns 20-21, you can see the Celesteela gets a special attack boost after getting a kill, while its 4 revealed moves are Leech Seed, Protect,Earthquake and Heavyslam. This could be an error and probably worth reporting I guess as it doesnt make any sense.
Grass STAB isn't one that's guaranteed. And, when I tried to reduce Thunderbolt/Volt Switch on the same set for occasions just like this, it didn't end well.
Trevenant has both. You rolled Phantom Force.
As already mentioned, Roserade has Natural Cure.