You are suffering from a killer one-sided crush, also known as "unrequited love", and there really isn't much you can do to change it into a relationship. I'll be blunt. You can not make somebody love you. You can't even make them like you. There are no magic spells or secret tricks that will make a person suddenly feel for you the way you feel for them. Love doesn't work like that (and thank the sweet stars above that it doesn't!). Love, when it is real and returned, is one of the most amazing feelings you will ever experience. Although it is hard to accept that this person doesn't return your feelings, it may help you to know that the pain you now feel will be erased from your heart when you find someone who does love you back.
Now back to the issue at hand, coping with your current crush. Since he has made his feelings for you clear, namely that he wants to be friends, you really only have one choice. You have to honor his feelings and wishes. You do however have options as to exactly how you handle the "friendship situation". You can swallow your feelings, move on and work on having "just a friendship" with this guy or, you can harbour your feelings and hope that the future will see your friendship turn romantic. Either way, the one thing you should do is actively take him up on his offer of friendship in spite of your deeper feelings.
Take heart, all is not lost! Friendship is always a good place to start. Right now he only knows a "one dimensional" you, as your friendship progresses he will come to see your many sides. With time, his feelings may even deepen into romatic interest. You say that the two of you are not in any classes together so it is entirely possible that his "Let's be friends!" comment is not a mere brush off, but a bonafide offer. He may want to start as friends because he doesn't know you well enough to have any deeper feelings (a sign that he is a good guy BTW), or he may be using the "friendship line" as a brush off (a sign that he is NOT a good guy BTW). You can't be certain which of these is true until you make a go of the friendship. Work from the premise that he really wants a friendship with you until he indicates otherwise.
By becoming his friend you get the opportunity let him see a new side of you, and you get to see a new side of him. In getting closer you may even fall into a relationship. Of course, the opposite is also true. As you get to know him better your crush, which is built on a fantasy not a reality, may disappear and you may lose interest in him. There are no guarantees that your feelings will stay the same through your burgeoning friendship. There are also no guarantees that his current feelings will change into love. After you become friends you may end up exactly where you are right now, in a one-sided love affair. But at this point in time, what have you got to lose? At the very least you gain a closer acquaintance and at the most you'll get your man!