I'm incapable of roleplaying. I always do what's right and never take on another personality than my own. And no matter how often I play through the game I always do the same things the same way. Any tips on how to roleplay?

Limit yourself.
Plain and simple.
You can't do that then maybe roleplaying simply isn't for you.
Create the character, imagine someone from a film or tv-series or create one from the top of your head.
And when you start playing, forget about what "you" want.
It's all about what the character wants.
Does he want to go over that hill?
No?
Then don't go over it.
Does he want to use a sniper rifle to sneak attack critical everything?
No?
Then don't use it.
Does he even want to accept the quest for Trudy or Joe Cobb in Goodsprings?
Does he even care about the town?
No?
Then don't do it.
He goes to freeside where the homeless ghoul is.
Does he want to respond to this guy in a friendly manner or a snarky manner?
Does he even want to talk to this person?
Does he even notice this person?
Let go of your wants and let the character come alive with how he/she wants to go through the game.
Just cause "you" know that there is a cool weapon in that cave doers not mean your character knows it.
Just cause "you" know that this NPC gives a quest does not mean he knows that or even if he wants to do it.
And again, if you can't do that, then maybe roleplaying isn't for you. :shrug:
Of course, there are always different definitions of what roleplaying is so if this post doesn't help you maybe someone else has a way of roleplaying that suits you.