Preheat oven to 450℉.
In a medium saucepan, combine rice, salsa, ½ teaspoon salt, and 1 cup water. Bring to a boil over high heat, reduce heat to low, cover, and cook 15 minutes or until liquid is absorbed. Take off heat and let sit, covered, 5 minutes. Fluff with fork and set aside.
On a large baking sheet toss 1 cup tomatoes, peppers, and onion with oil, chili powder, and remaining 1 teaspoon salt. Bake 15-20 minutes or until vegetables are charred and cooked through.
Finely chop remaining ½ cup tomatoes.
In a small bowl, mash avocado, garlic, and lime juice. Fold in tomatoes and add salt and pepper to taste.
To serve as a burrito: Spread ½ cup rice down the middle of a flour tortilla, top with ½ cup chicken, roasted vegetables, cheese, and guacamole. Fold in sides of tortilla then roll-up.
To serve as a bowl: Layer rice, vegetables, and chicken. Top with cheese and guacamole.
To serve as nachos: In an ovenproof dish, layer tortilla chips, chicken, and vegetables. Top with cheese, and bake in a 350℉ oven to melt the cheese. Serve with guacamole.