In respect of a realisation of the rotor assembly according to the invention for a permanently excited electric machine, it is preferred if the rotor assembly has a plurality of permanent magnets, which extend within a magnet pocket each, formed in the rotor core, so as to form a clearance extending in the axial direction. The cooling channel arrangement, in particular the third cooling channel, preferably extends through the clearances. The permanent magnets are thus cooled directly, so that the risk of demagnetisation is reduced, even in the event of full-load operation of the electric machine, and a high power density of the electric machine is attained. Due to the efficient cooling, the use of more economical permanent magnets with a low demagnetisation temperature with the same utilisation of the machine is also made possible. The permanent magnets advantageously can be free from rare earths, since the cooling strategy provided with the rotor assembly according to the invention eradicates the need for permanent magnets of this kind suitable for high temperatures.