In the last years, increasing interest has grown on the synthesis of light-weight, miniaturized surfaces for light manipulation based on metamaterials. These surfaces can be easily integrated in photonic systems and they can be used as high numerical aperture lenses, light-deflection surfaces and polarization-dependent surfaces. All-dielectric nanoresonator metasurfaces are particularly promising to synthesize light manipulating devices. By simply adjusting the geometric parameters (height and diameter) of the dielectric particles, it is possible to tune the spectral positions of the electric and magnetic resonant modes. The overlap of these resonances allows to design metasurfaces exhibiting a transmission coefficient with unit-amplitude and arbitrary, spatially-variant phase distribution. Moreover, resorting to asymmetric cross-section resonators, it is possible to define metasurfaces with high-efficiency of cross-polarization. In this work, we exploit both properties of dielectric nanoresonators to design a high numerical aperture micro-lens and a thin linear-to-circular polarizer, both working in the visible range. Numerical simulations of the performances of the devices are reported.