Welcome to CL as a brand-new poster.

I agree with the other posters that the most likely (but not the only) cause of roaches is food scraps being left somewhere in the car.

Putting some spiders in the car might help get rid of them (spiders eat roaches and many other insects for lunch)....but it might make the car unusable for awhile, unless you want a possible spider-bite yourself.

 

then put some wild birds in the car to eat the spiders,
then put a couple of cats in the car to eat the birds

 

Then a medium size coyote to eat the cats.

On second thought baits or a fogger sound like the way to go.

 

Hmmm............I've never tried coyote steaks.

 

No, not birds. Then there will be a big problem on the seats.

 

RAID!!!!!!!! Bomb that thing and not even open a door on it for two days. Serious. Worked for fleas in Mustang that I bought for a dime. Had to buy it tho. only $4250 with edelbrock heads alum driveshaft,spec stg3 clutch fresh 3.73's...oh, and V1 S-trim...all I had to was build a 347 to be happy.
P.S. The fleas were SERIOUS in this car.

 

My life's nightmare has become a thread on CL.