Abstract: Being one of the major food sources in the world, rice (Oryza sativa L.) has been studied to promote its growth and increase its production for the security of human livelihood. Since the root system is crucial for the growth, signal perception, hormone synthesis, water and nutrient uptakes, and production of a rice plant, the formation, development, and functions of the system need to be well understood. However, since the affecting factors are numerous, the study could be challenging. For instance, plant hormones are of special interest regarding their roles in regulating root growth and development under ever-changing environmental conditions. This article comprehensively reviewed subjects involving abiotic and biotic factors, related genes and regulatory networks, regulating plant hormones, and synergisms among hormones, metabolic trace minerals, and low-molecular substances. By emphasizing the studies on the plant hormones, it is hoped that research to further rice yield improvement and in-depth understanding of the basic biological mechanisms, complex interactions/interferences among biochemicals, and functional signaling pathways associated with rice root system development and functions will be realized.