Hissing roaches are among the larger species of roach so be careful when feeding them to your bearded dragon. Like it has already been stated, make sure the food item is size appropriate for your sized dragon.
There are smaller species avaliable. I personally raise lobster roaches. There max size is about 1 1/4- 1 1/2", allowing you to feed off the adults as well as babies. Some people consider them more upkeep then other species because they are very fast moving and climb smooth surfaces (glass, plastic etc). I dont mind though. I like how prolific they are! I am able to feed my 9 dragons from their established colony. Recently I even had to sell a bunch because they were overcrowding the 3 LARGE bins I have for them!
Here is a picture of one of my setups.
