Around day 42 of the first cycle of basil (aka: cheap seed basil), I pulled 7-8 plants from the hydroponic channels. I gave as many as I could away (with horrible luck, I think I got rid of 7). I also took a few plants and put them in various configurations in a kitchen window.
They are 55 days from starting from seed, and only 35 days of real growth.

Full grown basil
Here are the results:
This guy was simply cut at the base of the stem and put into tap water. I had filled the pint glass up to cover the stem base about 1/2″, and have since reduced that so that just part of the roots are submerged.

Cut basil root growth in glass
The roots are much thicker than the roots in the NFT system. And there are no root hairs. Maybe in its old age it can’t grow hair anymore.

Cut basil root growth
For the plant below, I cut the roots off from the rockwool cube. This was necessary because he wouldn’t let go of the spreader mat inside the grow channel. The roots had intertwined themselves fully in the fabricy-material.

Basil left in rockwoll in glass
You can see the bottom leaves are dead, and the little new root growth is all brown. The rest of the plant looks withered. He isn’t happy.
I did two plants this way, and both ended up looking pretty sad. They both received the same treatment and tap-water.
Adoption
The plants I put up for adoption seemed to fair well. I provided two plants that had a decent amount of roots come out nicely when removed from the hydroponic channel. I delivered them in a solo cup with a 1/4″ of water on the roots, and the rockwool still somewhat moist from the nutrient water.

Day 42. Mature basil roots
I had feedback on these two plants that a gradual addition of soil was received well, and they should make the hydro-to-soil transition ok. Should know more this week or next and I’ll post pictures.
Two other plants with similar rockwool and roots are happy after 10 days in just water. One was just planted into soil and the other remains in water. So this should be a good experiment as well.
Conclusion
Cutting the roots all the way off will kill the plant. But what is really surprising, is that cutting off the entire root ball by lopping the plant at the stem base seemed to fare as well or better as keeping a majority of the roots in tact.
This seems consistent with growers who take cuttings from strong plants (quite popular in the flower, tomato and cannabis growing community, but not so much in the leafy non-flowering area) and can have them producing fruit within 15-25 days with a simple branch from an existing plant (aka, the mother).