This seems like a good team, I'll try my best at rating it.
Togekiss
Baton passers tend to not stay out for long, so you should replace roost with thunder wave. This way you can take advantage of its ability, serene grace, more reliably.
Rhyperior
It's a good concept, but skarmory does it much better.
Skarmory @ Leftovers/Rocky Helmet
Ability: Sturdy
EVs: 252 HP / 4 Atk / 252 Def
Impish Nature
-Stealth Rock
-Whirlwind
-Roost
-Brave Bird
Use this instead. It should work better.
Serperior
I'd say serp's not tanky enough for this kind of set, but... It actually is. 75/95/95 defenses is actually really good. I'd be surprised to find this kind of serperior in. OU.
Slowbro
Perfect.
Magnezone
I'm assuming togekiss will be passing into this. If so, I could imagine it being a real threat. Also, in case toge dies, run modest to get as much power out of it as you can.
Dragalge
Also perfect.
Overall, this team is looking really good. Only a few minor tweaks are needed. I hope I helped!
