Does a water softener help keeps roots out of sewer line?
Nothing short of calling RotoRooter and drilling those roots out will keep them out of a sewer line, and that too is only for a while. Copper Sulphate doesnt work, that is because your sewer is pitched and the water drains downward so fast that the Copper Sulphate has no time to react with the roots. Salt, will do noting to those roots. I question whether or not you even have roots in your sewer line. Most sewer lines are at least 8 feet deep underground, and tree roots do not go down that deep.. You probably have an older tile sewer and one of those tiles has shifted about causing a cave in of the line. If you have a septic system, those can be penetrated by tree roots quite easily, there is no solution other than cutting down trees such as sugar maples which have a tendency to do this this.
