Bilayer films Fe/Tb having sharp (Tb on Fe) or having rough (Fe on Tb) interface and multilayers of these were prepared by molecular beam epitaxy to study the interlayer magnetic coupling. Their magnetic properties were characterized ex situ by ferromagnetic resonance, polar magneto-optical Kerr effect and magnetization measurements. Atomic Force Microscope (AFM) was used to measure the roughness of quartz substrate. Perpendicular magnetic anisotropy (PMA) was observed in bilayers with rough as well as sharp interface and the anisotropy energies were estimated. This was compared to anisotropy energy in multilayers. It was also observed that demagnetization factor depends on the substrate roughness and should be considered in the FMR data for these ultrathin films.