The roadside is the strip of ground along the edge of a road — the grass, the dirt, sometimes a ditch. You wait at the roadside for a bus; wild flowers grow by the roadside; a stall might sit at the roadside selling fruit. As an adjective it means “happening or sitting there”: a roadside café, a roadside memorial. It is a plain, useful word. Though actually it is not the paved path for walkers (that is the pavement or sidewalk). Roadside is the edge of the road itself, and the bit just beside it.