Getting a college roommate is random chance.
Sometimes you get lucky, and sometimes you get a pony.

Rainbow Dash enrolls at an Earth university.

Update: and then some other stuff happens.

Celestia who? That tall, awkward schoolfilly?

Applejack is using her pre-maternity leave to take a vacation on Earth. Her husband doesn't trust humans, but when she unexpectedly goes into labor there's no time to go to an Equestrian hospital.

It's about Mr. Bean in Equestria.

Or perhaps Cheerilee is Batman?

Bruce Lee didn't die. He just went to a land of magical ponies. Then he solved all their problems.

Twilight's job in the Equestrian Army puts her under enormous stress. Perhaps a certain pony can help her relax.

On a boat.

Tagged for sex just to be safe.

What if the Mane 6 were motorcycles?

Special Forces working dogs are highly trained, just like the men they serve with.
When the Russians need a veterinarian, they call Fluttershy.

What do you do when you've been turned into a vampire?
For Cheerilee, the answer is "get a second job."