Ferromagnetic nanorods play important roles as active fillers in multifunctional composite films. Many composite films used as inductors and antennae, as recording media, or electromagnetic (EM) filters and polarizers, require the nanorod alignment in a certain direction. The strategy for the in-plane alignment of nanorods has not been established yet. Since the composite assumes a multistep processing when the material rheological properties change in time, in situ characterization of the film is required. Magnetic rotational spectroscopy (MRS) with ferromagnetic nanorods offers flexibility and accuracy providing desired spatial and temporal resolution in characterization of submicron thick films. Herein, recent progress in understanding of the basic physical principles is presented guiding the nanorod alignment in thin films by external magnetic field and characterization of these films by MRS.