I don't know if you can get it where you are, but I have found that Boric Acid is by FAR the most effective killer of cockroaches. It's the only thing I have ever used that, as soon as I used it, I didn't see another single roach that year.
I am obsessive about those sickening fuckers, they are the one creature on this earth which truly revulses me, and I will not stand to live in a house with them. If you have to, just get the roach traps and keep a clean house, especially your kitchen, around the stove and refrigerator and where you eat.
And DON'T eat food in your bedroom for God's sake. They seek it out. But if you can, get that boric acid. It works.