This paper deals with the problem of plotting the robust root loci of a feedback control system which includes affine parametric uncertainties in the coefficients of the plant transfer function. First, based on a geometrical interpretation of the value set of a family of affine parametric uncertain polynomials, an efficient algorithm is proposed for checking whether the set includes the origin of the complex plane. This zero‐inclusion test algorithm is then applied along with a pivoting procedure to trace out the boundaries of the cross sections of the robust root loci. Since the proposed technique of generating a robust root locus needs not to construct all exposed edges of the value set in testing the zero inclusion condition, and needs not to use a brute‐force two‐dimensional gridding approach in plotting the boundary of a cross section of the robust root loci, its advantage of saving computational cost is obviously significant.