Can I replace wheat flour with pistachio or cashew flour and get good results in bread and or roll dough?

Nut flowers do not contain enough gluten to produce good results in bread or rolls.

I only replace some of the flour.  I made pizzelles last weekend and added pistachio flour but I think it was about ¼ - ½ cup total.  I also use it to make Frangipane and replace all the almond flour with pistachio flour.

I find pistachio flour tends to clump, so I process it in the FP with regular flour before adding it.

Pistachio pizzelles sound delicious.