The problem of reconstructing in a quantitative fashion dielectric objects embedded in a layered medium with possibly (unknown) rough interfaces is dealt with. In particular, a nonlinear inverse scattering technique is proposed as a suitable tool for giving an accurate imaging of homogenous targets. The proposed approach, which exploits multifrequency data, is not limited to the weak scattering case. Moreover, a simple method is proposed so that simultaneous reconstruction of both unknown permittivity and roughness profile can be performed. In order to assess effectiveness and accuracy of the proposed approach under actual field conditions, a small number of antennas placed on a short measurement line is considered. A large number of numerical simulations confirm the effectiveness of the inversion approach, as well as its robustness with respect to noise on data and approximate knowledge of background parameters.