I breed chameleons and starting the babies on dubia roaches contributes to their health. I've had great sucess feeding dubias with the following method:No dubia because I already have those and he doesn't seem to like them too much.
[1] Introduce small dubias around 1.5 months. Place them in a small container and just let the chameleon observe them. You will throw out many at this stage.
[2] When the chameleon is around 2.5 months I begin placing dubias on the enclosure's screen. The chameleon will observe them running up the screen and will begin to recognize them as prey.
[3] Once the chameleon begins eating the dubias that are running up the screen you can present them in a container.
Since your chameleon is older try starting at step 2.