Thin films with high thermal conductivity are urgently needed as heat dissipation materials for electronic devices. In this study, we developed a readily scalable roller coating method followed by ultra-high temperature annealing to prepare large-sized, free-standing, and flexible reduced graphene oxide (rGO) films with high thermal conductivity. The in-plane thermal conductivity measured by a laser flash method for the sample annealed at 2800 °C was 826.0 W m-1 K-1, which was much higher than that of copper foil. X-ray diffraction, Raman, and SEM analyses indicated that, different from common chemical reduction, heat treatment at high temperature could not only remove O, H, and other impure elements but also develop the in-plane crystal size of graphene and decrease the interlayer spacing of graphene sheets. Meanwhile, tight embedding during annealing and concomitant mechanical impaction was indispensable for retaining the shape and raising the density of the films. Furthermore, molecular dynamics analyses demonstrated that point defects, pentagonal/heptagonal defects, or even large in-plane holes in graphene could be rehabilitated to a great extent during ultra-high temperature annealing. In addition, real-time temperature monitoring demonstrated that the rGO films could act as an excellent thermal dissipation material in LED packages by reducing 10%-15% of the temperature increase.