1-2 per role is definitely the better option unless you are really good with certain champions.
There are quite a few champions that can play every role decently. Lulu, Kayle, Gangplank, Heimerdinger, Lee Sin, Elise.
I didn't include stuff like Warwick there because if you try to play Adc or support Warwick you will most likely get 4 man reported if you lose the game.
Then you have a bunch of stuff that can play at least 4 roles decently. Jayce, Nidalee, Kennen, Karma, Riven, Maestro Yi.. list goes on.