1. Preheat oven to 500°.
2. Combine first 5 ingredients in a heavy-duty zip-top plastic bag. Snap off tough ends of asparagus. Remove scales with a vegetable peeler, if desired. Cut asparagus spears in half. Cut mushrooms into quarters (or in half, if small). Add asparagus, mushrooms, and, if desired, sesame seeds to vinegar mixture; seal bag, and turn to coat vegetables well.
3. Place vegetables in a single layer on a 15 x 10-inch jelly-roll pan. Bake at 500° for 10 minutes or until tender, stirring after 5 minutes.