The first time I showed Spike a dubia she was so excited and ate it up so quickly I thought I was introuble. At the time I was only starting my dubia colony so I wasn't able to feed just the roaches - I was afraid she wouldn't touch the crickets. she went to the crickets with no problem. When I finally had enough dubias I showed her one and she went right for it, eating about 6 to 8, one right after the other. The next day she acted as though she had no interest - wouldn't even look at one. The day after that she was back to going crazy over them.
You gotta understand, they are beardies and they seem to know they are spoiled. Plus, if they are interested - crazy time... if not, it will be as if your not even in the room. Don't freak out if your bd doesn't take it right away, although I really don't think you will have a problem!
I started out feeding Spike like one dubia every few days or so with the crickets, as my colony grew bigger I added more dubas to her menu. I have been told to try and stay away from letting them eat one right after moting, or while they are white. They are softer and more tender at this time - kind of a filet minon to a regular steak. The lady I got my dubias from says her bd will only eat the white ones, which I am sure is a major pain!