Cockroaches are notorious for being hard ... the Wondercide Flea and Tick spray will do the job. The post The Best DIY Gnat ...

COCKROACH CONTROL: Advion Cockroach gel bait from Syngenta is a high-performing bait product targeting many pest species of cockroaches including German, American and gel bait-averse cockroaches ...

so I think there's still plenty of room for us to keep working.