Sven Dust.
Seriously, this stuff is the best to keep roaches away. You need to have at least a bottle with you all year if you have a bug problem. Place it around the door, creases in the walls, holes in the floors, basically anywhere a roach can squeeze into. I keep some around the entrance to my door just in case.
Bay Leaves
I'm not joking. This stuff works wonders. I was told this trick by my father who had many apartments with roaches. Place the leaves in holes, creases, anywhere a roach will try to get into. They hate the smell of these leaves.
Boric-Acid
This works good too but is costly. We used this once and it kept the bugs away for months. Spray in dark places and wet places (Bathroom, behind washers/dryers, under sinks) etc. Wash hands after use because it is poison. If you own pets, DO NOT USE (unless you keep animals away from acid)
Basics:
Bugs come into apartments/dorms usually because it's messy. So, stop being messy.
- keep counters clean of crumbs/food
- get rid of clutter since they like to hide in dark areas
- take out the trash since they will most likely to be drawn to the smell of rotting food
- have cleaning days with roommates, someone clean an area of the apartment to prevent the bugs from returning
- mop floors with bleach and water to get a strong smell in the apartment, they will most likely leave
- have pipes checked out (we had roaches in our bathroom because of pipes, and they were crawling through there. We used bleached to kill the ones remaining in the pipes. If you use bleach run it down with hot water so it won't smell bad)