Honestly... pretty much everything. The jungle is extremely different even to what it was in Season 4. I haven't been around long enough to know what the Season 1 meta was, but here's some stuff:
Top lane: Tank/Fighter(bruiser?). CC tanks Gnar and Mao'kai are some top picks, unless you're in Solo Queue and then you mostly see Riven, Darius, and some marksmen, because people like trying to carry.
Jungle: There have been EXTREMELY recent changes to jungle itemization that have made AP junglers (Elise, Evelynn, Nidalee) some of the top picks. Additionally, there's Devourer. And we don't talk about Devourer. We watch it demolish our team while we all try to attack this one GOD DAMN RENGAR WHO WILL NEVER DIE BECAUSE HE IS LIFESTEALING MORE THAN WE DO TO HIM AND HE KILLED OUR CARRIES BEFORE THE FIGHT BEGAN!!!!!!!!
Okay, I'm better now.
Mid: AP carries, most mages, and assassins. If somebody is heavily AP, and don't have a specific other role to go to, they're mid. Additionally, even if an assassin is AD (Yasuo, Talon), they go mid. EXCEPT FREAKING RENGAR!!!!!!
Kats R evl.
ADC: The role where every marksman except Urgot, Quinn, and Teemo go. Because they're trash at ADC. Or, in Quinn's case, just trash. In any case, marksmen go here, buy either Infinity Edge (for most ADCs), or T-Force (for AP-using ADCs like Corki), and feed off of the other team's bot lane.
Support: They engage, disengage, or heal things. Most champions with high CC but low base attack stats go support. Engage supports like Alistar and Thresh are at the top right now, and Zilean is at the bottom. Because he isn't good.
Dragon: Gives you stats. 1st: Damage; 2nd: Damage to towers; 3rd: Move speed; 4th: Damage to minions; 5: Doubles all of that for a short time. Expires on death as well as after 3 minutes.
Baron: Gives you 3 minutes or a single life of up to 40 extra AP & AD, faster recalls, and ridiculously powerful minions when you are near them.
Smite: Smiting jungle camps gives you things.
Summoner spells: You bring Flash every game. If you are Top, you bring Flash/TP. If you are JG, you bring Flash/Smite. Most ADCs bring Flash/Heal. Most supports bring Flash/Exhaust (Flash/Ignite is better in a kill lane). Mid is where all the other ones are used. If you are an aggressive 1v1 mid laner, pick Flash/Ignite. If you are expecting a lot of ganking to kill your enemy laner, pick Flash/Exhaust. If you are expecting a lot of stuns (against Twisted Fate or Annie, for example) pick Flash/Cleanse. If you are expecting a lot of enemy ganks to kill you, use Flash/Ghost or Flash/Barrier, depending on the opponent. If you're trolling your team, pick Clarity/Clairvoyance because those spells are useless.
If you have any specific questions, I can answer them. Probably.