This Stickied Thread is where these kinds of posts should go, you don't need to make a whole new thread. I'll explain the Pokemon Roles for ya.
Physical Sweeper - A pokemon with a good Attack stat and a physical Attack movepool. It needs good Speed stats too.
WEAVILE is a good example for a physical sweeper. its Attack and Speed stat is enormously high. A Physical Sweeper's goal is to take out as many pokemon as possible with full power attacks.
Special Sweeper - Its the exact same thing as a physical Sweeper except it utilizes its Special Attack stat and needs a big Special attack movepool. Also a good speed stat.
GENGAR is a good example of a special sweeper since its Special Attack and Speed stat is high and can take out a fair amount of pokemon.
Physical Wall - Sometimes called a Physical Sponge. A Physical wall needs to be able to wall physical attacks very well. It needs to withstand a large amount of attacks thrown at it. A Physical Wall needs a good Defense stat. A good HP stat is also needed. A good example of a physical wall is
STEELIX because its defense stat is enormously high and is able to take a large amount of Physical Attacks and survive
Special Wall - Also called the Special Sponge. Its the same as the Physical Wall but it withstands more Special Attacks. It needs a good Special Defense and HP stat to be effective. A good example of a Special Wall is
BLISSEY because its HP stat is outrageously high and its Special Defense is skyrocketing.
Tank - A pokemon that can withstand a fair amount of attacks while still being able to inflict damage. It usually doesn't carry a good Speed Stat (though it would be nice). A tank pokemon carries a good HP Stat, a Good Attack Stat / Special Attack Stat, and a good Defense / Special Defense stat.
Spikespinner - A Pokemon that can set up Spikes, Stealth Rock, Toxic Spikes, or have access to Rapid Spin.
Baton Passer - A pokemon with a wide range of stat boosting moves (including Sub, Mean Look, Swords Dance, etc.) and have access to Baton Pass.
Cleric - a Pokemon with access to Heal Bell or Aromatherapy.
Hazer / PHazer - A pokemon that has access to Haze, or a PseudoHaze(PHaze) move like Confuse Ray, Leech Seed, Whirlwind, etc.