Okay, here we go -->
Beedril
First off, I think you meant to have 252 evs in speed instead of special defense.
Also, for the moveset, I would recommend protect instead of knock off only because Beedril is super frail and he needs the speed he gets from mega evo. And, as for nature, I would personally go for Jolly, but if you prefer adamant to hit harder, I think it wouldn't be too bad.
Finished set looks like this
Beedril @ Beedrilite
EVs: 252 spe, 252 atk, 4 hp (Adamant/Jolly)
Moves:
Poison Jab
U-Turn
Drill Run
Protect
Skarmory
Nature and EVs pretty standard, nothing much to say. However, the moveset could use some elbow grease:
Skarmory @ Leftovers
EVs: 252 def, 252 hp, 4 spd/atk (Impish)
Moves:
Stealth Rock
Whirlwind
Brave Bird/Drill Peck Brave bird for extra power, drill peck if you really dislike recoil
And as for the last slot, I would go for roost, or maybe defog. If you really want spikes, you can replace whirlwind, but this is my recommended set
Rotom
This is definitely an original set, but I think it has some merit, if not any:
Replace shadow ball with will-o-wisp - If you want to actually abuse the scarf, you can, but typically in OU you use trick/scarf to ruin chansey and sort
Change 252 spd evs into 252 spe, and you can try it on showdown.
Finished set:
Rotom Wash @Choice Scarf
EVs: 252 spe, 252 spa, 4 hp (Timid)
Moves:
Trick
Hydro Pump
Volt Switch
Will-O-Wisp
Latios
Latios has merit as a defogger as well, so if you are not using defog on skarmory, replace Surf with defog. Latios also has access to recover, which I highly recommend.
Finished set looks a bit like:
Latios @ Life Orb
EVs: 252 spe, 252 spa, 4 spd (Timid)
Moves:
Draco Meteor
Psyshock
HP Fire/Defog
Recover
Conkeldurr
Looks good, only thing is that you might run poison jab for clefable and sylveon, two checks to conkeldurr
Set:
Conkeldurr @ Assault Vest
EVs: 252 atk, 128 spd, 128 hp (Adamant)
Moves:
Mach Punch
Drain Punch
Knock Off
Ice Punch/poison jab
Blastoise
You could run a mized phaser, but it is generally better to stick to the special side
Blastoise @ Leftovers
EVs: 128 spd, 128 def, 248 hp, 4 spa (Whatever nature, really)
Moves:
Rapid Spin
Ice Beam
Roar - Roar allows you to stay in on ghost types and phase them so you spin hazards away
Scald - Scald has that burn chance, STAB
All in all, this is a good team!
Hope I helped!