I haven't much to say. This is a very good team, overall. I can give some advices:
Politoed
The EV spread I would use with it is the following: 252 Sp.Def / 2552 HP / 4 Sp.Atk. It would make Politoed bulkier than before.
The moveset changes: I would use Scald > Hydro Pump and Toxic > Hidden Power [Grass]. I prefer the bulky Politoed over the tank one.
Toxicroak
OK, this one is fine, although I would go for Jolly > Adamant for the extra unexpected speed.
Tentacruel
OK, this one is perfect, I would just say Hasty > Timid so that Rapid Spin can deal with severely weakened Pokemon. You know, if this is for Showdown use, Showdown is occasionally bugged, so that 3 % remaining HP could be removed by Rapid Spin, although the case is rare. Then, you could use Timid > Hasty. The one you prefer most you will use.
Jolteon > Vaporeon
I mean, with BulkyToad, you have exceeded the number of suggested bulky Pokemon on a team. Jolteon is exceptionally strong in the rain ; it has a high speed with a great special attack.
Try:
@ Choice Specs / Air Balloon:
Trait: Volt Absorb
EV: 252 Speed / 252 Special Attack / 4 HP
Modest Nature
- Thunder
- Volt Switch
- Hidden Power [`Ice`]
- Shadow Ball
Thunder hits tremendously hard with Jolteon's investment and specs, and now, in rain, it bypasses da nasty accuracy check to become strong as da Blue Flare Reshiram.
Volt Switch is primarily here to scout on your opponent's movesets and items, while securing Jolteon. You can also use it to finish a weakened Pokemon if you need at the same time to bring out another Pokemon.
Hidden Power [`Ice`] is ultimately for the Bolt-Beam combo, although it's not as strong as Ice beam.
Shadow Ball provides some extra coverage, especially against Lati-Twins and Alakazam.
Finally, Choice Specs can be replaced by an Air Balloon so that Jolteon has no weakness, but it will be weaker.
Dragonite
Your Dragonite moveset is really not bad, but the EV in speed, I would put them in HP, so that multiscale become harder to face.
I believe that either Surf or Outrage > E-Quake should be more reasonable so either you have a hard-hitting move or a STAB.
Roserade
Not much to say. Just Choice Scarf > Black Sludge for 2 causes:
- Roserade is too frail for Black Sludge and
- Roserade is too slow to compete with other OU threats.
Extra Advice: You cannot know when you will face Foul Play Pokemon so I suggest you to put 0 IV in attack for every special attacker but Tentacruel.
Hope this help !