This work deals with the design of parallel cable-driven robots having more cables than degrees of freedom (DOF). Compared to parallel robots with rigid links, this issue has a distinctive property: the requirement of keeping the cables taut. In this paper, it is shown how numerical tools, recently introduced elsewhere, can be used to solve the important practical problem of finding geometries of robots such that a given prescribed workspace is fully included in the wrench-feasible workspace. Then, in order to improve the solving procedure of this problem, it is shown that another workspace is of interest: the wrench-closure workspace. Some of its relationships with the wrench-feasible workspace are highlighted.