So basically ill post what we should already know but its always good to have a topic like this.
AP/AD carry - both should take dorans as 1st items, one should go mid and one bottom, should have either ghost or flash to escape (only exceptions for champs who have already flash like ez etc.)
Tank - well tank can do jungle but I prefer to see tank do a solo top lane, should always monitor opponent builds and counter build those who are fed most, should initiate a fight and try to disrupt/disable opp carrys but also protect his.
Offtank - can also solo lane, should have a decent amount of health while still bringing nice dmg in team fights - this can be a jungler(someone like udyr).
Support - should always take clairvoyance as a summoner spell and try to monitor opp jungler with it for a possible counter jungle, buy a lot of wards, eventually buy oracle if tank didnt and heal heal heal.
Jungler - be able to counter jungle, always take smite, ward opp blue/red, have a decent ganking abilities, have some health so you have a better survivability(most junglers are melee), wriggles lantern is a basic item for a jungler
some of these are facts, some are my opinions. post yours if you have something to add.