A rotor assembly for an electric motor for a turbomachine defines an axis of rotation. The rotor assembly includes a jacket member that is hollow and that defines an inner radial surface facing inwardly toward the axis of rotation. Furthermore, the rotor assembly includes a magnet member that is received within the jacket member. The magnet member includes an outer radial surface facing outwardly from the axis of rotation. The jacket member is made of a sintered composite material having carbon filament and a sintered matrix. Additionally, the inner radial surface of the jacket member abuts against the outer radial surface of the magnet member to retain the magnet member in a radial position relative to the axis.