When to transplant seedlings to system. New to hydro

[JibbaJoe0129]

So this is my first time trying to grow with hydroponics (or really grow anything at all) and I started simple with Basil and Parsley. I started with 1.5" rockwool cubes and seeds. Now the basil has started growing leaves and so has the parsley and i have the cubes under a grow light for half of the day. One of the basil plants JUST started poking a root out of the bottom of the cube. Im finding mixed opinions online, some say transplant to system now and some say wait longer.

My plan is to use the floating raft method. So should i transplant the cube to the raft with the cube just below the raft touching the water, or should i wait until the roots are longer and the plant is larger? the leaves are very small still, maybe 1/4inch at most. Any help and advice would be awesome