Heat oven to 450. Line a 13 x 9 -inch rimmed sheet pan with nonstick foil.

In a small bowl, combine hoisin, soy sauce, vinegar, sesame oil and sriracha. Set aside.

Place bok choy, peppers and shiitakes on prepared sheet pan. Combine 3 tbsp of the hoisin mixture with canola oil. Pour over vegetables and toss to coat.

Toss shrimp with remaining hoisin mixture. Place shrimp over vegetables.

Roast at 450 for 20 minutes. Garnish with sesame seeds and, if using, scallions. Serve with additional soy sauce if desired.