##The approach you take to the game is wildly different, when you play different roles.
ADC - generally focus on cs until late game. some will sacrifice cs for lane trades. they never worry about roaming, unless you're in high elo.
very kill-oriented class. entirely based on in-combat micro, and positioning. managing minion wave is also very important.
Top - easy to tunnel vision. constantly brawling with opponent, but usually tanky enough to not die from it. need to be a good 5v5 engage late game. can fill roles ranging from peel-support, to unstoppable bruiser.
good timing for engage and disengage very important. usually has the tools they need for most any 1v1 or 1v2 fight.
counterpicks influence this lane dramatically.
Mid - usually play damage dealers, and are most effective when they roam to assist other lanes. need to constantly worry about ganks, due to a very open lane, and often ward better than other roles. AOE abilities mean that managing minion waves is much easier than other roles.
Needs map awareness, and good use of AOE's, and the ability to disengage.
Jungle - looks at the game similar to a game of chess. needs to know exactly where the enemy jungler is (despite not being able to see them) all game long. needs to plan long in advance (due to map travel times) where to focus their attention and gank, and where not to. needs to "rescue" failing lanes, snowball wining ones, and counter an opponent they can't even see.
You are also responsible for the neutral objectives.
Support - your job is to play god. don't worry about killing anything, your allies are more than happy to do that for you. you decide who dies, on both teams, and when. in order to do this you need to know what is happening in all lanes. you need to engage enemies, use cc, and heals, and are the only player who specializes in disengage.
You have more responsibilities than anyone else, and (just like god) you doing a good job usually means that things "magically" work out for your allies, whether they attribute this to you or not.
I've arranged the list from the top, who are more micro focused players, to the bottom who are more macro focused players.
I readily admit that I understand mid lane least, because I play that role least.