I can't believe no one has said much in this post.

DO NOT remove the rockwool! The roots are growing all through that thing. If you try to remove it you will simply tear most of your roots off the plant and kill it. Rockwool is intended to stay on the clone. In hydroponics like Ebb & flow. The cube is often the plants ONLY decent support in the grow rocks.

In the future if you don't like using the rockwool, use dirt.

As for removing the plastic. You can if you like. You'll need to when your ready to move it to a bigger pot, But if you want to veg in there longer leave it for now(keeps the water in the plug).