a roll - up type portable roadside sign of the type normally used with a resilient stand member . a novel warning flag mounting system is disclosed for such sign wherein the warning flags are retained in association with the sign such that they are collapsible with the roll - up sign cross members and remain attached thereto . such mounting is achieved by pivotably attaching the warning flag poles to the substantially vertical cross member of the sign . a rotatable support bracket is also attached to the cross member and includes a pair of spaced curled ends which receive the warning flag poles such that they extend substantially upward and are disengageable therefrom in order to permit collapsing of the sign assembly . the support bracket is rotatable such that it assumes a position substantially collinear with the remainder of the sign components , enabling the entire assembly to be quickly and conveniently stored . an alternative embodiment is described wherein means for mounting a third vertically extending warning flag rod is provided .