Radar echoes produced by a target contain the target motion information and physical characteristics. In a stepped frequency (SF) signal, a range-Doppler coupling occurs where the movement of the target affects the target range profile. Using this characteristic, in this paper, an algorithm for estimating the size and rotation vector of the rotating target is proposed. For this, we consider a distributed radar system to utilize target-sensor geometry. By executing signature extraction from the high resolution range profiles (HRRPs) on time-range images and two nonlinear least squares (NLS) estimations, the desired parameters are successfully estimated. Through several simulations, the performance of the proposed method is analyzed and the favorable results are obtained.