Binaural signal processing algorithms for hearing aids are often first evaluated on binaural signals that are synthesized by a room acoustics simulator. This eliminates the need to acquire real binaural room impulse responses during the design phase, which would be time-consuming. Moreover, it gives more control over the binaural signals and avoids acoustic noise. Room acoustics simulators, however, are computationally very intensive, and their complexity and level of realism is usually reduced to make them usable for research purposes. In this paper, we give a brief overview of existing room acoustics simulation methods. Next, we investigate how accurate room acoustics simulators must be in order to be perceptually convincing, and to be a valid substitute for real measurements. Finally, we propose a room acoustics simulator that is sufficiently realistic and computationally efficient for research into binaural signal processing algorithms.