theres a cheap easy solution i have been using for over 10 years.
just mix rocksalt with hot water like a 25 pound bag every 4 months, do twice in spring befor trees leaf out thats when max root growth occurs.
kills the roots doesnt harm tree, really cheap too. do before leaving house so rock salt water remains in line as long as possible.
or you can go high tech where the line is snaked and cleaned then a interior sock is placed and inflated with very hot water, it hardens the plastic sock no more roots can get into the line. but its costly.
incidently its not just trees that get into lines, even bushes can. I had some fitzer bushes the plumber claimed were in my line. didnt believe him till fixing a wall showed the roots went straight down to the line.
i installed a basement toilet and found under my floor roots everywhere, i had to use a saw and lopers to install the drain for the toilet. its hard to believe.