To add more protein to this vegetarian dish, fold drained and rinsed canned black beans into the rice mixture. Or serve it with Soupy Black Beans.
Preheat oven to 450 degrees. In a medium saucepan, bring 1 1/3 cups water and 1 teaspoon salt to a boil. Stir in rice and chipotle. Return to a boil; reduce heat to a simmer. Cover; cook until rice is tender, about 45 minutes. Remove from heat; let stand, covered, until dry, about 15 minutes. Fluff with a fork.
Meanwhile, in a roasting pan, toss bell peppers and carrots with oil and chili powder. Season with salt and pepper. Roast, tossing occasionally, until vegetables are fork-tender and lightly browned, about 30 minutes. Remove from oven; toss with spinach to wilt.
Warm tortillas according to package instructions. Dividing rice, cheese, and vegetables equally among tortillas, wrap burritos. Serve with salsa, if desired.