Did the plumber scope the line after he removed the obstruction. I ask because it's very easy for roots to continue to invade and damage the sewer line. If the roots found their way in through a joint or coupling odds are good it will happen again and actually cause physical damage to the line. A tree only needs to be within 50 to 100 feet to find a water source like a water or sewer line. Odds are good the line had a leak even if very small (it's like a rodent finding food). The RootX is a temporary fix.
The line has been scoped before, and shown to be mostly intact, but there is a point close to the connection the municipal system where it kinks, and even transitions from plastic, to a clay segment. But that was done at least a couple years ago, and the current situation is unknown.
The driveway will be needing replacement sooner rather than later, so when that's redone, the lateral can be exposed and addressed as needed.
No experience here. Both Root X and Roebic foaming root killers contain the active ingredient Dichlobenil herbicide. Root X seems to be the gold standard that others are compared to. Beyond it's active ingredient it claims to have better adjuvents to increase it's effectiveness. An A.I. inquiry of cost effectiveness is actually interesting and helpful (if believed). It claims that Root X works the best, especially early on when getting control over the roots. It implies that once controlled and relatively clean, the Roebic "might" be good enough and cheaper.
Both are annual (maybe more) herbicide treatments to manage root intrusion. I did not study copper sulfate treatments, another alternative. $100 +/- a year to manage a potential huge expense is not too bad.
My choice would be to use the Root X and continue monitoring.
Interestingly, RootX says their 2 lb product will cover 50 ft of 4 in pipe. Roebic claims that their 1 lb product will cover the same distance. I suppose, for $20, it's possible to double up on the Roebic, and still come out ahead.
I've seen reference to Copper Sulfate before, but I guess it's not considered environmentally friendly.
In the longer term, all of these are practical band aids, but it will still take a lot of plumber visits, at the apparent rate of need, to equate to the cost of an excavation and repair.