I've come up with a pretty good method. I use a pair of hemostats since I dont like to grab the roaches. I can grab one carefully from the can I have the calcium dust in and place him on the side screen. As long as they dont have something to run and hide under they will keep moving on the screen until they reach the top. My male ambilobe always picks them off before reaching the top. I guess this method would not work if your cham won't eat in front of you. I can also hold the wiggling roach in front of him with the hemos and he will grab it from there as well. I do that for supers.