No, Dettol does not keep rats away.
The cockroach will not cause harm that is experienced when stung by an insect.
Insecticides, baits, traps, and/or environmental modification can be used to control infestations of cockroaches.
Vinegar diluted with water is a reliable, natural homemade ant killer.
Insecticides and cleans identified especially for spiders, along with natural repellents like peppermint oil, can help maintain spiders away.