Borax (laundry aisle) mixed in equal amounts with powdered sugar and sprinkled around where the roaches congregate is the best thing I have tried thus far. The roaches are attracted to and eat the sugar coated borax and die as a result. But make sure its in an area where you don't have a dog or cat to lick. Behind fridge, in cupboards, on the counter behind a tv, etc. This same techinique works quite well against those seasonal ant infestations, as well.
As for silverfish, which I have never seen, let alone be infested with are listed on my bag of diatomaceous earth of critters it kills. It's the remnants of ancient microscopic sea critters, and their shells are glass-like and slice open a small insect and they die. It works great for mites, fleas, sow bugs, ants, and other small bodied insects. Its not a chemical and poses absolutely no danger to humans or pets. I have used it with great success in chicken houses by dusting the chickens with it and sprinkling it around the floor of the house and in their dust bath areas. Apply it the same way as the sugared borax.
On a side note, this is the second thread, that I can recall, of you throwing a minor temper-tantrum because people don't answer your questions promptly. Most people probably have no experience on the matter. And some, like Hurley, don't like rewarding childish behaviour. And some like myself, check the forum sporadically. I just now got dinner put away, the kitchen cleaned up, laundry done, chickens put to bed, lawn mowed, and just now sat down to read more posts and reply. I, for one, do not click on the "New Posts" button. I read throughout the day and answer when I have the time or if I have any insight on the question asked.
A little patience goes a long way in my experience. Answers will come when they come. =)
The roaches and silverfish are non-threatening to your snakes, just an annoyance. Black Knight is still available locally for me, although I have never tried it, as I've never had any infestation worthy of a mass-extermination spray. Plus I don't like using chemicals if I don't absolutely have to, so I usually go the more naturalistic and less poisonous routes like I described to you above.
Good luck either way.
