Following work of Mustaţȃ and Bitoun we recently developed a notion of Bernstein-Sato roots for arbitrary ideals, which is a prime characteristic analogue for the roots of the Bernstein-Sato polynomial.Here we prove that for monomial ideals the roots of the Bernstein-Sato polynomial (over C) agree with the Bernstein-Sato roots of the mod-p reductions of the ideal for p large enough. We regard this as evidence that the characteristic-p notion of Bernstein-Sato root is reasonable.