Very possible. There was enough of an urban Roman population for Berber petty chieftains to move in and declare themselves "Roman kings." Unsure about Mauretania but in Tunisia, a Romance dialect did last until the 12 century even centuries after the initial Arab invasions.
It's quite feasible for sure. Eventually the Roman population would be Berberized, but not before a fair amount of Roman influence spreads to the Berbers.