The road noise could be from the tires, or possibly from the wheel bearings.
With some brands of tires, the amount of road noise increases significantly when the tread is half-worn or more. Since these are probably the original tires, that means that their effective tread life is no more than 30k-35k, so it is likely that they are about half-worn by now.
I assume that you had your mechanic check this car before you purchased it, so on that basis we can probably eliminate bad wheel bearings as a source of the noise, but then again…