As a vegetarian, I've always found that rice and tofu act as great meat substitutes, containing sufficient protein for my body's growth. Is this true?

Rice with tofu is a good feed for a vego. However you need to understand that the biological value, or the amount of usable protein is much less than for dairy based products. Rice and tofu also do not supply the ideal ratio of Calcium and phosphorous, whereas WPC (Whey Protein Concentrate) does. Find a product high in WPC such as Perfect Protein. Scientists recently rated WPC as the protein source with the highest Biological Value and PDCAAS, outscoring such food sources as meat, eggs, spirulina, casein & soy.