Grilled Vegetable Hand Rolls

Name: Grilled Vegetable Hand Rolls
Ingredients: 1 cup sushi rice; 1 tablespoon seasoned rice wine vinegar; 8 ounces asparagus spears; 4 mini sweet peppers, halved and seeded; 4 to 5 shiitake mushrooms, stems removed; 1 tablespoon olive oil; 2 teaspoons low-sodium soy sauce, plus more for serving; Freshly ground black pepper; 1/2 cup shredded red cabbage; 1/2 cup shredded carrot; 1 mini cucumber, halved, seeded and sliced into thin strips; 1 avocado, pitted, peeled and sliced; 4 nori sheets, halved into rectangles; 1/2 cup bottled sriracha mayonnaise; Sesame seeds, for sprinkling; 1/2 cup sushi ginger (pickled)