It’s very common for a sewer to have roots in it. Don’t let high pressure sewer contractors trick you into buying a new sewer system just because you had sewage come up in your tub or shower one time.. Instead get it cleaned out when the problem arises and use the frequency of those problems to gauge the necessity of when to replace the sewer.
Sewer contractors often use your fear to sell you a new sewer and while you’re in an emergency state of mind and they convince you that you need a new sewer while in fact that may not be the case at all.
You may also want to consider a pop-off/up cap at your clean out or get a clean out installed to lessen the effects on your life and to let the waste water issue arrive outside of the home rather than inside where it can be quite alarming and unsanitary.
In short, clean your sewer when needed and don’t jump to conclusions by replacing it just because contractors said that you need to.