Whats the best way to kill tree roots?

Rock salt will kill them plus what plants that are around them.

Source(s):

A tree surgeon told us to make ridges going both directions in a tree stump amd put rock salt in the ridges to kill it.

Drill some holes in the tree roots and fill them with table salt. Inexpensive and you wont take a chance on killing anything else or contaminating your soil.
or
best way to kill any tree is to cut a 1 inch gash all the way around the circomferance of the tree. the tree may look fine for several months but it will certainly kill it....
whatever you do, do not use chemicals

cut them and pull them out in manageable sections , and them just be vigilant , otherwise you might ask an arborist