I definitely learned a lot about you from this, and it was interesting to read. I'm not sure if you should be more serious or matter-of-fact, either (I'm doing this question too - and no, I'm not going to give you bad advice), so I'll just give you grammatical advice. What I changed is in [brackets]. Good luck! (who knows - maybe we'll end up rooming together)
Dear Future Roommate,
Hi, roomie! I'm Ryungnam Kim. No need to strain your tongue[,] though, because I go by Hannah instead.
As you might have noticed from my last name, I'm Korean and I'm [an] FOB (just in case, it stands for Fresh Off the Boat, meaning I'm a foreigner). And I am not ashamed that all my friends always called me a "hard-core-Asian," however they meant it. I guess they were pointing at my fluency in Korean and Japanese and obsession of K-pops and [standing/position as] the president of Japanese National Honor Society and all. But don't worry, I can speak English fine! No, more than just fine. Although I sound like someone you'd have to use body language to communicate [with], the fact is, all my friends though[t] I was native born American until I told them otherwise. So no worries.
I must admit that I'm pretty random. Let's say you and I are watching a camel fight on TV. I might suddenly stand up and walk up to a la[p]top, sit in front of it with a grave expression on my face, and start Googling "Israel current issue" and looking through [the] CNN newsroom for a further reporting on how Israel and Egypt are getting along. [And] that's only the beginning of my so[-]called "artsy impressionist side," as my friends put it. [needs transition here] So I hope you'[ll] understand me if I go, "(blank) reminds me of (blank)" quite often. I have this weird tendency to connect two completely different [things], especially colors, like oil paintings of scenery, to people and classical music. [But please] don't be alarmed [-] I'm not crazy. In fact, my friends find my explanation for randomness quite amusing and say that ["]it kind[-]of makes sense, but not really["].
But [the] bottom line is, I'm easy to get along [with]. And I'm really sympathetic [(I] cry whenever I watch Titanic[)], and good at listening while keeping my mouth shut about what I hear. So I hope [you]'ll like me[,] and [I hope'll we'll be] Best Roomies Forever!