This is more of a concern if you do not eat meat. Vegans often hafve to mix and match foods in order to obtain complete amino acid profiles in their diets. Beans bring a certain fraction of some types of amino acids, while rice brings others. If you combine them, you can end up obtaining a complete amino acid profile in a single meal, much like if you ate a serving of meat or dairy or eggs, etc.
Not sure which beans you need to combine with which types of rice though. Are you vegan? If not, I wouldn't sweat it and would say try to opt for real meats anyways - especially red meat for growth. It has other things like creatine that are beneficial for anabolism.