Could seal the Pc with tape so only the fans allow air in/out, but seriously, get the roach guys in man,
OP would need screens over the fan ports as well as any ventiallation openings on any part of the pc.
Then theres those ultrasonic bug repellers... I dont know if they really work or not. I used to live in an apt bldg long ago and the upstairs tenant had roaches. I had the place fumigated the first time I saw one and the exterminator gave me a large box of roachproof powder and told me to spread some under my front and back doors and make sure its always there. Plus I had to wash and dry absolutely everything.When I moved out 6 months later I think I was the only roach-free apt. LoL
The OP probably has a rodent problem as well, roaches eat mouse poo so get rid of the mice and the roaches will be easier to eradicate.
Years ago, one of my office-mates at my company brought in a new computer he had just bought the previous week, to show off to all us nerdy types on our lunch hour. Apparently he had left it on during the weekend in his kitchen at home, because while he was proudly demonstrating some game on it, a roach crawled out and scurried across his desk. We all burst out laughing and making jokes about 'buggy' hardware. Next morning when I came in, he had spread 3 full cans of "Roach-Pruf" all around his desk, my desk, the carpeting, furniture, etc. Then that afternoon while I was making phone calls he let off an aerosol bug bomb in the middle of the room, necessitating immediate evacuation. Pretty hard to explain to the client why I had to hang up and run in the middle of our conversation...
All our boss did was wag his finger (fore, not middle) at my officemate and tell him not to do it again.. Sheesh..