Don't worry if you lose roots. It can't be helped and I have seen an incredible flush of new roots after a "trimming". I would say if you can salvage as much as 1/3 of the roots you will be in very good shape. The only difficult part is if this is not the season for the plants to form roots. If no new roots form when you move it to a new tree then you may need to put something around the existing roots that will conserve moisture. Good luck and keep us all informed.