Combine 2 cups of water, rice and salt in a small saucepan. Bring to a simmer, and cook, covered, until all of the water is absorbed. Let the rice stand for 10 minutes and fluff with a fork.
Preheat oven to 400ºF (200ºC).
Heat the beans in a small saucepan over medium heat. Stir in 2 tablespoons of the olive oil, 1 tablespoon water, cumin and cayenne and let simmer for about 5 minutes. Remove from heat and set aside.
Toss the sweet potatoes in the remaining olive oil and spread in a single layer on an aluminum-foil-lined baking sheet. Season with salt and pepper then bake until golden brown and cooked through, about 20 minutes.
In a small sauté pan over medium heat, add the soyrizo and break it into pieces. Cook, stirring occasionally, until cooked through and lightly browned, about 10 minutes.
To serve: Divide the lettuce between two large bowls. Scoop ½ cup brown rice into each of the bowls then divide black beans over the top. Add the sweet potato and soyrizo to the bowls then top with guacamole, pico de gallo, sour cream and pepitas.