entomology - Why do cockroaches flip over when they die?

This question has always mystified me since young. For beetles, I can reason that they flip over because they have a higher centre of gravity causing them to be in unstable equilibrium when they tuck in their legs when they are about to die. For cockroaches with a lower profile, I would expect them to stay upright. But why do they flip over? Is it more comfortable for them to die this way or is there a scientific explanation for this?

Edit:

As noted in some of the comments below, this is a general observation based on cockroaches being killed by insecticide. I haven't got the chance to observe (or notice) cockroaches that die in other ways and therefore do not want to limit the scope of my question to just insecticide poisoning.

Answer

It is a result from the insecticide you are using. From this excerpt from the 10th Edition of the Mallis Handbook on Pest Control:

Neurotoxic insecticides cause tremors and muscle spasms, flipping the cockroach on its back. A healthy cockroach can easily right itself, but without muscle coordination, the cockroach dies on its back. Cockroaches exposed to slow-acting insecticides that target respiration (energy production) also can die “face-down,” as they run out of energy without experiencing muscle spasms.

Here's also a website from UMass describing it in more detail:

Most of these insecticides are organophosphate nerve poisons. The nerve poison often inhibits cholinesterase, an enzyme that breaks down acetyl choline (ACh), a neurotransmitter. With extra ACh in the nervous system, the cockroach has muscular spasms which often result in the cockroach flipping on its back. Without muscular coordination the cockroach cannot right itself and eventually dies in its upside down-position.

And an entomology professor even answered this for Maxim:

Most insecticides are poisons that target a bug’s nervous system. When you spray a roach, those neurotoxins cause tremors and muscle spasms, which flip it onto its back, and without muscle coordination, that’s the position it dies in