I had the same problem, I bought some clones from a local dispensary and they all came in rock wool cubes. However when I tryed to remove the rock wool on one of them, disaster, it pulled the roots out!
I still put it in the cloner to see if it will resprout roots, and it's only been 4 days so I'll keep an eye on it. As for the others, I just stuck the whole cube in the net pot and put the neoprene collars ontop, you kinda have to squish the rock wool a bit to get it to fit in the small 2" pots. They all seem to be doing fine as of now.
Only issue I see is over watering since the rock wool acks like a spoonge. If you have an adjustable timer, try going longer than 1 on 5 off since the rock wool is absorbant. Other than that, once the roots hang down several inches outside of the pot, it doesn't matter, go back to 1/5.
You can try to cut away some of the rock wool, but be carefull!
Oh yea, and of course remove the plastic wrap on the rock wool, or else it it will block most of ur sprayers.