The surface characteristics of graphenes and carbon-based nanofillers are analyzed regarding activity, porosity, and roughness in comparison with mechanical and dielectric properties of polymer nanocomposites based on graphene in a nitrile–butadiene rubber (NBR) matrix. From adsorption isotherms of the fillers, information about surface area, roughness, and surface heterogeneities is evaluated. In addition, different models are used to evaluate a pore-size distribution. The composites are prepared in a conventional way by melt mixing. These graphene-based elastomer nanocomposites are mechanically and electrically characterized and compared with a standard carbon black. It is demonstrated that graphene nanocomposites show a considerably different behavior compared with carbon black, although the properties strongly depend on the graphene type. Promising results for industrial applications are found in the case of graphene/NBR composites containing dioctyl-phtalate (DOP) as a softener.