This paper presents a new approach, named Rotation Invariant Subcarrier Mapping (RISM), to Peak-to-Average-Power-Ratio (PAPR) reduction in OFDM systems. This technique enables data transmission over those subcarrier which are dedicated to the PAPR reduction if a state-of-the-art method, Tone Reservation, is employed. We apply RISM to DVB-T2 systems, showing that the reserved tones foreseen by the standard only for PAPR reduction purposes can effectively carry additional useful information to the receiver, and, at the same time, RISM achieves a PAPR reduction very close to the Tone Reservation. Thus, the proposed technique offers improved spectral efficiency while keeping the robustness against nonlinear distortion effects.