hi nadia,
try this one it really works,
make a dough with one cup of flour mix with half cup of boric powder,(i bought it from shoprite), pinch of sugar,with water and make small balls of this dough place them where u see coakroaches at night, inshallah next morning u will see the difference, if not u can repeat the process..and leave those balls for few days.
all the best
regards