A rotor bearing assembly for an underwater generator of a fluid flow power plant includes a hollow cylindrical bearing carrier configured to be inserted into an interior of a rotor and releasably connected to the rotor such that they rotate together and an axle journal extending into an interior of the bearing carrier and rotatably supporting the bearing carrier. The bearing the axle journal and the bearing carrier are configured as an installation unit such that a portion of the bearing carrier is insertable into the rotor interior and removable from the rotor interior while attached to the axle journal. Also a generator including the rotor bearing assembly.