I usually use something called textured vegetable protein (TVP). It is a soy based protein used by vegetarians. I get it in the health food section of my grocery store.
Never feed roaches a high protein diet. Stick with 15%, 20% tops, above that and you will start having some die offs. They are not crickets that can still do well at 30-35% protein diet. If you feed the roaches too hight of protein, they will store the extra as uric acid. Guess what happens when a lizard eats too much uric acid, Gout.
That's odd. NY Worms specifically says to feed a high protein diet http://www.nyworms.com/dubiacare.htm
Anyhow, I only mix it in with my dry gutload at about a 25% ratio. My roaches seem to love it. The one I use has 12 grams of protein per 1/4 cup which equals 25% of the daily recommended intake for people. Not sure if that is considered high for roaches, but I was under the impression they needed a moderate level of protein to breed well. Am I wrong?
I dont have the info in front of me (wrong pc) but look up the development of bug burger and uric acid studies in dubia roaches. basically dubia do not do well above 15% protein, bug burger was 30% (really good for crickets) and was killing off roach colonies slowly if it was only fed bug burger. They had to reduce it down to 20% protein, and say feed them lots of veg too.