Pinworms spread by shedding ova (eggs) in the feces. These eggs get spread by any puddles the feces may encounter at the bottom of the cage and hitch a ride with any feeder insect that may come along. They are easily spread by human hands doing any sort of maintenance on the cage. Your feeder insects are not going to have any pinworms infectious to chameleons unless your hands introduce them. The good news is that this means a major strategy of breaking the lifecycle is, literally, in your hands. Pinworms could also be spread by poop that bounces off a plant or branch on the way down or when the chameleon rubs its cloaca against a branch and then licks it sometime later. There are many possibilities. Pinworms (all of our parasites) have had millions of years to evolve ways of getting back into a chameleon in the vast expanse of the Madagascar forest so a 2x2x4 cage is a cake walk.
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This is a pinworm ova and is very common in chameleons. (I actually have a series called "pinworm of the week")
Strongid is a brand name for Pyrantel Pamoate and is commonly used against nematodes like pinworms. It acts on nematodes in a different way then Fenbendazole (Panacur) but has been used for decades. Neither are new. Trust your vet as far as medicine and dosage. I have always used Fenbendazole and there is no harm in asking to try a different drug, but that is not likely to be the thing that needs addressing. With both drugs, it may take more applications to get the infection down no matter what medicine you use. The overwhelmingly, most likely reason why the infection continues is because your chameleon is, somehow, getting fresh ova.
I would suggest you treat all of the chameleons for the sake of eradicating the ability for you to unknowingly transfer ova from one cage to the next. It is true that a minor amount of pinworms is not a health issue to the individual chameleon, but as long as there is a chameleon producing ova somewhere in the house managed by the same hands that work with the other chameleons you will have transmission risk and won't be able to reliably guard against a reinfection. I know we all like to think we are careful in our maintenance, but these are microscopic. They can bounce off of the poop when it hits the floor and be on a cage surface away from the poop that your hand brushes against when you are cleaning up the poop. It is very difficult to know where the ova end up so the best approach is to simply treat all chameleons that show pinworm infection until they all have three negative fecals. And during this time take the cage to quarantine level where the floor is completely clear and no branches or leaves are under any other branches where the chameleon could poop from. Strictly supervise feeding to ensure nothing gets away and takes a walk on the bottom of the cage.
But don't cull your feeder colony. Chameleon-infecting pinworms are not reproducing in with your roaches. Your roaches have it only if the ova are transferred from your chameleon's cage. If you are interested in further reading on parasites and feeders here is a study where someone tried to figure out if parasites came with feeders. But, even beyond scientific studies, the pinworm lifecycle just does not include roaches for anything other than a convenient ride when a roach walks through the puddle that poop touched. But it is good to read what study has been done.
An Evaluation of the Gray Cricket, Acheta domestica, as a Source of Oxyurids for Reptiles
