In our own little world-

Although I can't directly compare, I'd imagine being an RA is like being heavily involved in greek life, where separate buildings are different fraternities and sororities. Just like greek life, buildings are arranged in pairs (according to location and style). Also, during the application process, you must go to several rounds of interviews and a social, and then you receive one bid that you may accept or decline from one building. And after a few years of working the job, you pretty much know every other RA.
Another similarity to greek life is that the different dorms each have their own reputation of people they will hire. Just like greeks want to make sure you can party, the HD (Hall Director) wants to make sure you can handle what goes down in their neck of campus. The following list will include each residence hall, their RA type, and why they need that type. Rated PG for posterity.

Freshman (Underclassmen) Buildings-
Life in these buildings vary.
--It might be that your building is filled with all "Undecided" majors. In which case your RA will most likely be a hardass that is on your shit all day. But don't stress, this is because you are probably in a building with kids with no ambition and only time to kill. Hello saranwrap.
--Or it might be that your building has all academically oriented majors, such as nursing or engineering. These building are usually nicer, because the college knows kids won't mess things up. In an instance such as this your RA will be timid and have no life. Probably because there is no need for discipline in the building. These buildings also tend to be smaller, which mean less RAs and more time on-call. Shitty.
--You could live in a horrible rundown warehouse. This is entirely possible. The way to check if this is your building: when you walk down your hallway, does it feel like it could be the inside of an insane asylum? If yes, your building sucks. RAs here usually do not give a shit and are lazy as hell. Why bother when some freshie is going to drunkenly mess things up in 5 seconds anyway?
--You might get lucky and live in a middle of the road building. These building are usually a random assignment. If you live here, rejoice! Your RA is probably the perfect mix of mostly gone and around when you need them.

Upperclassmen Dorms-
Ugh.
--These building tend to be horrible. They are old and run down, but usually the sophomores and juniors that live here are too drunk to notice anyway. The people that RA here are wicked chill. Smoking pot and drinking on weeknights? Just keep it down, guys. They don't need to deal with your alcoholism and theirs.

Upperclassmen Apartment Dorms-
Woot! These are lovely! If you live here, congrats, you either are fantastically connected or play a sport. Please don't light shit on fire in your kitchen, it evacuates the whole building. RAs here are the cream of the crop. There are no newbs in here, everyone knows what they are doing. That being said, they usually aren't around because cool kids live off campus. This is where I work, and while most of the hilarity occurs in Underclassmen housing, there is some quality shenanigans going on around here too.

Graduate Apartments/Alternative Housing
These housing options are for those folks that can't stand the normal hoot and holler of regular residence halls. Graduate housing? Geez, get a real house, you're old! But RAs here are usually just a bit off. Like how you put the misunderstood abstract painting in the back room where no one goes. Alternative housing RAs are super accepting. Just tell them you are going through a sexual identity crisis or something. They don't care, they have their own cook up here.

So that's basically the RA layout, and you can take my opinions for what they're worth. 2600 yen. That's $29.25 American.