Preheat oven to 400F. Grease a large baking sheet or line with foil/Silipat. Toss together all the ingredients in a large mixing bowl until well-coated. Spread onto prepared baking sheet. Bake for 20-25 minutes, stirring halfway through, until vegetables are softened and meat is cooked through. In the meanwhile, cook pasta and make dressing.
To make the dressing: Add all the ingredients in a food processor and blend until smooth. Thin the dressing out with reserved pasta water, 1 tablespoon at a time (I used ¼ cup total)
To serve: Toss pasta with fajita meat & veggies and dressing. Serve with cheese, if desired. Squeeze some fresh lime juice for extra freshness.