oops forgot you said for a frilled dragon anyways, the adult roaches are about the size of a Florida roach commonly referred as a palmetto bug, 20 won't go to far and for the price I'd breed my own, like i said i got a 1000 shipped for 145 and they where already producing, I got a dark sterilite like footlocker trunk
http://www.sterilite.com/Category.html?Section=Storage&ProductCategory=34 like 15 bucks at walmart, I like these because They have 2 strong latches on each side plenty of room, and has place to attach a lock, I drilled 1/2" holes close together creating a grating of like 8" x 8' on each end , Then i used greenhouse screening and hot glued a big enough piece of screening inside of each end so that now i have a bunch of ventilation holes backed with the screen (I prefer drilling the holes then screening rather then cutting out a big piece and then just covering the one big hole, yes it takes longer but I found it offers better stability with my feeder boxes and i Can easily stack smaller boxes without fear of knocking the screening out, also i prefer the greenhouse screening compared to regular window screening because it's a finer mesh, it was designed for keeping out the little bugs, keeps them in great to, I have no idea where to buy it though, my neighbor builds greenhouses so i'm able to get what i need just from scrap pieces left over) Heat mat under one side, water crystals from here
http://www.watercrystals.com/ real Cheap that way a pound of the cheaper shipped for under 20 Bucks makes like a year supply of cricket drink. My opinion you'd be better off just forking out for 500 to start with set it up like i said cricket flats on side of heat mat, just take the bulk of the males out as u see they're starting to accumulate and other to feed with, put them in something else to gut load for 2 or 3 days before feeding and that's it, your set up producing your own the only thing you should need to purchase is more water crystals when u start to run low, like i said i have 10 beardies at the moment and not one of them even hesitated the first time i fed them them dubia, they don't make all that noise, don't have the stench,or bad mortality rate of crickets, more nutritious and easier then crickets, truly a win win. I highly recommend them for anyone that isn't held-back with the whole squeamish factor of keeping and maintaining a roach colony