How are you defining intelligence? And how would you measure variance of intelligence across cockroaches in a way that is relevant to a way that you measure intelligence across humans?
Of course, I have no idea how a brain works, and it's unlikely that it's anything like a computer.
That seems like a reasonable definition.
As a result, I think it's reasonable to say intelligence in humans is a lot more varied than intelligence in cockroaches. There are some humans who will never be as productive as the least productive cockroach. On the other hand, there are some humans who will create things more profound than the most productive cockroach.
I assume I know what makes a cockroach productive...obviously I don't, but it's seems reasonable to me to assume that cockroaches haven't had their version of cockroach-on-the-moon moment.
The day they do, we may be in trouble!