Though I have never researched specifically that, I have seen trees and other plants growing through granite. Roots are amazingly powerful. Add to this, the plants only need enough root structure in the media to 1) Not fall over and 2) Get into some of the nutrient solution. I wouldn't expect a problem with these rocks, with regards to whether or not the roots will be able to get through them.

If, however, price is your concern, may I suggest growstone? I have it in my system now and I am really happy with it. It doesn't drain as fast as the hydroton I used in my last set up but it is lighter and doesn't leave your water dirty.