Reduced graphene oxide (r-GO) nanocomposites are very useful for different applications such as magnetic storage media and bio-imaging/biomedical applications and recently have been found to be very useful in electronic and magnetic resonance imaging contrast agent where r-GO was functionalized with silica coated gold and iron oxide nanoparticles. The potential material for these different applications was established by experimental data where the microstructural, electronic, electrical and magnetic properties were studied. In the present study, we have compared the electronic and magnetic properties of these nanocomposites (r-GO: Au NPs & r-GO: Fe2O3 NPs) using different experimental data. The data is verified with density functional theory (DFT) calculations to elucidate the relationship between the density of state (DOS) and their magnetic properties. Coupled with the experimental data, the DFT studies revealed that the magnetization enhancement of rGO: Au-NPs is mainly due to the nano-sized clusters with addition of Au 3d and O 2p orbital states as contributors; whereas that of r-GO: Fe2O3 NPs is mainly due to Fe 2p, Fe 3d and O 2p orbital states as contributors.