A rotor assembly, including at least one driven member, e.g., a compressor rotor, and at least one driving member, e.g., a turbine. At least one rotating thermal insulator rigidly attached to either the driven member or the driving member. A coupling feature that includes mating geometric surfaces on the driven member and the driving member, wherein the geometric surfaces are configured to allow radial sliding, relative centering, torque transmission, and axial constraint between the driven member and the driving member.