[quote=Rare]
This might seem dumb, but what roles are there? I never have played anything similar to League of Legends, but I had played multiplayer in Battlefield 4 and Team Fortress 2. Is the roles similar to the ones in Battlefield 4 and Team Fortress 2?As for 'laning and farming', are they similar to spawn camping in Battlefield 4 and Team Fortress 2?
[/quote]

The roles are twofold.
[b]Lane Roles:[/b] Top (Top lane), Mid (Mid lane), Bot (Bot lane), Jungle (Exactly as implied, though you shouldn't start on this role.)
[b]Character Roles:[/b] Mage, Fighter, Assassin, Tank, Support, ADC/Marksman, etc.

Most often it's a Bruiser top, Tank or Assassin jungle, Assassin or Mage mid, Marksman bot, Support bot.

Mages are most often known for their burst potential: How much damage they can do in three seconds or less. They hit you hard once and then wait to charge their abilities and hit you again. They also sometimes have crowd control. (Explained further below.)

Tanks are most often known for being very heavily armoured and having a lot of crowd control. (Crowd control stuns, slows, or otherwise incapacitates an enemy so that your team can kill them or escape from danger.)

Fighters are a hybrid: They have the defensive stats of tanks but the damage of marksmen/mages. They aren't superior to tanks at dealing with damage or marksmen at dealing damage, but mix the best qualities of both to have some survivability and damage output.

Assassins do exactly as implied: Get in, kill a target, get out. They're like mages but they capitalize specifically on squishy or important targets, like marksmen.

Supports exist solely to help their team by giving buffs, heals, using crowd controls to slow or stop the enemy, and so on. They're most often paired with marksmen in the bot lane, as marksmen have fragile early games, but a lot of late game damage output.

Marksmen are also often known as AD Carries (Attack Damage carries). They start the game out weak but become powerful late game with extreme damage outputs that no other class can match, however, they're glass cannons, and need a team to protect them.

Over time these intricacies should become pretty simple to understand. For instance: Nasus is a tank-fighter, he goes in top lane, but can jungle. Vladimir is a burst mage, he goes in mid, but sometimes goes top as he also has a lot of health which makes him a solid fighter. Vayne is a marksman through and through, and goes in bot lane with Soraka, who can heal and give mana to her allies.