Prep - Spray cold grate of outdoor grill and utensils with grilling spray. Prepare grill for medium heat.
Combine - Stir together vinegar, sugar, salt, pepper, mustard and celery seed in medium bowl. Add broccoli coleslaw and toss to combine; cover and set aside.
Create - Grill franks 5 to 10 minutes or until hot, turning frequently. Toast inside of rolls.
Place franks in rolls and top each frank with 1 tablespoon barbecue sauce and 1/3 cup broccoli slaw. Serve immediately. Extra coleslaw may be served on the side or with another meal.
Tip - The broccoli coleslaw may be made several hours before using. Cover and store in refrigerator.