What’s the rate of call for the roto-rooter on the main drain. Was that the first time you called. If so, you might want to investigate some products that go into the drain to disolve tree roots.
But it may be too late. Most of those products are best used before you have a problem.
If your house uses clay pipe to connect your main drain to the sewer line, you may have to replace it. That’s an ugly and expensive job, but better than having it in your basement!
If your neighborhood has experienced storms recently, there is a slim chance that there could be a clog in the city line. Most towns will send a crew to check for clogs on the city owned lines for free, when you can to report a problem.
Good luck