If roaches are necessary for life on earth to continue ...... we are in good shape!
Cockroaches are important, as are many creatures. Mostly to the food chain.
VIRUSES are the really important 'death' forms. (I would have said life-form,but VIRUSES aren't ALIVE unless there is food).
Guess what 'form' of creature was the FIRST on planet Earth (as far as we can tell)?
How do you 'kill' a creature that spends much of it's time DEAD?