Combine rice and 4 cups of water in a medium saucepan over high heat. Bring to a boil, reduce to a simmer, and cook until water has been absorbed and rice is tender, 20 to 25 minutes.
Stir in soy milk, maple syrup, and vanilla; cook, stirring, for 5 minutes more. Divide between serving bowls. Garnish with walnuts and cinnamon.