What Pokemon roles are on a competitive team?

Answer 1

A good team should have Sweepers and Walls.

Sweepers will have either a high special attack or physical attack stat, and high speed. They are designed to KO as many of your opponent's pokemon as possible, by dealing the most damage possible, while taking as few hits as possible. Common sweepers include Latios or Scrafty.

Walls are used to check your opponents sweepers. They will have either a high physical defense or special defense stat, and high HP. They will have supporting moves such as Toxic, Protect, Recover (Roost, Moonlight, Wish etc.), Roar, Taunt, Substitute, Thunder Wave etc. Their purpose is to prevent your opponent's sweeper from dealing any major damage to your team, by soaking up their hits while dealing damage to them through statuses, or consistent damage like Seismic Toss. Common walls include Jellicent or Ferrothorn.

Other less common roles include Tanks, Phazers, Annoyers and Leads.

Tanks will generally have a high attack or special attack stat, and a high defense or physical defense stat and relatively low speed. Are made to take hits and dish them out. While not being able to do either as well as sweepers or walls, the fact that they can do both makes them good. Common tanks include Heatran or Tyranitar.

Phazers are anything that can change the flow of your opponent's team. They can prevent them from setting up using Mist or Taunt, or counter Substitutes using Roar or Whirlwind.

Annoyers tend to be luck-based and, well, annoying. They will typically run moves like Thunder Wave, Confuse Ray, and any moves that have a high flinching chance. They will typically have high speed. A common annoyer is Sableye.

Leads aren't used as much in 5th Gen play anymore because of the Team Preview before a match. They are still a valid option and are designed to scout out your opponent's team. They will typically have U-Turn or Volt Switch, some kind of entry hazard like Spikes or Stealth Rocks, and they might even have Fake Out. They will typically have high speed.

There are many other different roles, and everyone's team is different, so be aware of the less common Dual Screeners, Shufflers, Baton Passers and Condition Setups.

Dual Screeners carry the Light Clay and will have Reflect and Light Screen.

Shufflers will have Circle Throw, Dragon Tail, Whirlwind, or Roar, and are designed to annoy your opponent and kill their pokemon through entry hazards.

Baton Passers are relatively self explanatory, and pass stat boosts to sweepers on your team that could benefit from them.

Condition Setups will set up weather conditions through use of Rain Dance, Sunny Day etc. or Trick Room.

Hope this helps. Pokemon has a complicated metagame, but it's quite fun once you get used to it~!