Most Helpful Guy
It depends what he wants in a particular partner. It can be in the head for a guy who is more emotionally interested in a woman, maybe not so if he's just in it for the sex and is not emotionally interested. He may like you enough to be friends and likes the sex, but that's as far as it may go with him.
Most Helpful Girl
If he says he just wants friends with benefits then you need to take his word for it and believe it. I don't think there's any way you can make him want a relationship when he doesn't want one. If you want a relationship with someone, I suggest you drop this guy quickly and go find someone who does before you get hurt.