1Heat gas or charcoal grill. In medium bowl, toss fennel, radicchio and apple. In small bowl, mix oil, vinegar, honey, salt and pepper. Pour dressing over fennel mixture; toss to coat. Set aside at room temperature or refrigerate until serving time.
2Place hot dogs on grill over medium heat. Cook uncovered about 10 minutes, turning frequently, until hot. Add rolls, cut sides down, to grill for last 2 to 3 minutes of cooking time until toasted.
3Spread mustard on cut sides of each toasted roll. Place grilled hot dogs in rolls; top with slaw.