If the roots were rotten then you have root rot and nothing will save them. There is no cure for root rot and it stays in the soil and will infect anything else you put there, even next year, unless you do something to kill it off. I would solarize the soil where they grew, by putting on black plastic and letting the sun kill the organism.

It is still early enough to buy plants so I'd get some and plant them in very large pots

If the reason the roots rotted was because they were too wet for a long time, I don't think you will have a problem planting other tomatoes there later. That is a physical problem, not a disease. If on the other hand, the poor conditions stressed the plants and then they succumbed to disease, then Oilpainter's suggestion is a good one.

You could try rooting some of the branches with growing tips in those very large pots that Oilpainter mentioned. Cut a branch off, trim off most of the leaves leaving just a few at the top. Poke a hole in your potting medium (or even in the ground if you want to experiment or you think the roots just drowned) put the nekkid stem into it, firm the soil/medium around it so that it makes contact with the stem and keep the soil/medium fairly damp for three or four days. Putting them in the shade is a really good idea. When the leaves stop drooping you can water normally and move them into the sun. They will not need to be hardened off since they are already outside.

That would be a good way to replicate your plants, especially if the variety is not available locally or the choices are slim pickings like they are in many places. I have used this method many times with great success.

Bets

Only 2 out of 14 plants have actually died. 3 are growing, but the leaves have not returned to normal. The others are alive but not growing. It seems to me that if the roots on those had rotted that they would have died too. I have started rooting some suckers.