I had a section of my clay sewer line replaced with PVC pipe around 10 years ago. Things appeared to be fine, then it backed up a couple of times, so I've been doing annual maintenance (sewer line cleaning) due to fear of backup and to remove tree roots. This year after they cleaned the line they did a free camera through the sewer line and it showed roots at two sections, misaligned (no more than an inch I think) where the line replaced with PVC pipe connected to the old section of sewer line and looks like a belly in the pipe where waste sits until flushed through pipe. They are suggesting installing permaliner for $6635. Do I really need to do this? Can I just use root killer twice a year to keep the roots out?

The permaliner will not cure the bbelly so I'd get 3 bids on a complete retrenching and new PVC line to the street riser

Here's some help on the roots.
Going in, let me say that sooner or later you're going to have to bite the bullet and replace that old sewer line with PVC. If you wish to control roots RootX or Robics Foaming Root Killer that contain Dichlobrnic are two products you could try.
A less expensive way would be to call around to garden supply stores and ask for fine grain Copper Sulphate. Put a 1/2 pound in your toilet and flush it down. Repeat in 6 months.
Hope this helps and thank you for rating my answer, Tom

With little efforts you can do it yourself and save a bundle...

Excavate and expose the PVC section of sewer
Expose both PVC to CLAY connection
Replace with new PVC
Replace both connections ( here use approved connections like Fernco Fittings made for this type of installations )
Refill trench

Make sure new PVC pipe is properly supported so it won't cave in during refill again...

Depends how handy you are, you can do the whole job for couple hundreds of dollars

Good Luck... Milo