"The host isn't returning our calls. He
finally comes around the next day.
We tell him that we are leaving and that we can't stay because of the roaches.
He claims that roaches are just a part of life in Texas and are completely normal.
He does give us back $160 dollars in cash though and tells us he will give us the rest later when he gets it. He says he will keep in touch"
Sorry, but I think you're being unreasonable by asking for too much. It's the same as the adage about Fast/Good/Cheap--pick two, you can never have all three. It sounds like the owner was busy, not avoiding you--he comes over the next day and that's avoiding? He gives you part of your money back and doesn't lie about the issue. I'm failing to see a problem here.
I also find the entire story highly exaggerated: An apple that we bought and put on the counter had been cored out by what I imagine was an army of roaches that night.
----
"When I see him he tells me he moved back in and took the place off airbnb and doesn't feel he owes us anything because we should have sucked it up and dealt with the roaches.
I say I will feel it was fair if we pay half, and he says life isn't fair."
Again, this is completely reasonable. He owes you nothing, you didn't sign a contract. You had unrealistic expectations that under any circumstances would have been disappointed no matter what the situation.
Edit: I'm becoming more convinced this story is entirely fake to begin with looking at what questions the OP has chosen to answer/ignore.