Killing Cockroaches Safely
Borax and DE are a low coast and easy way to eradicate insects. They both are a less toxic form of killing bugs. DE is the remains from a prehistoric sea mollusk (the shell I believe) while Borax is a natural occurring mineral.
Borax should not be applied where it can get accidentally inhaled or absorbed by humans and non-target animals. Although it is less toxic than other insecticides it is not inert and can have harmful effects if ingested.
DE while having no toxic ingredients also cause problems due to it's shape. The fine powdery dust that is DE has extremely sharp ,albeit minuscule, edges. If enough is inhaled  it can cause possible lung problems.
To haphazardly spread either of these substances while considering them safe, is both reckless and unsafe. If you'd rather not tempt fate and sleep easy purchase a trap-like product (like &quot;Roach Motel&quot; etc.). These products either use a lure phernome that entices the specific bug to enter the enclosed trap where upon it gets stuck on the sticky floor or a chemical bait that it ingest's and dies. This is the safest way to ensure you and pets are safe and insects are eradicated quickly.