Preheat the oven to 400°F (200°C). Line a large sheet pan with foil or parchment and lightly spray or brush with oil.
Make the teriyaki marinade: in a small bowl whisk together 1 teaspoon sesame oil, grated garlic, grated ginger, soy sauce, rice vinegar, and brown sugar until combined.
Place the salmon fillets in a large zip-top bag, pour in the marinade, seal, and refrigerate to marinate for 10 minutes.
Meanwhile, in a large bowl toss the broccoli florets and halved mini peppers with 1 tablespoon sesame oil, 1/4 teaspoon kosher salt, and freshly ground black pepper to taste.
Spread the seasoned vegetables in an even layer on the prepared sheet pan and roast for 10 minutes.
Remove the pan from the oven, toss the vegetables, and push them to one side to make space for the salmon. Place the marinated salmon fillets skin-side down on the sheet pan, reserving the marinade.
Return the sheet pan to the oven and roast for an additional 7 to 8 minutes, or until the salmon is just cooked through.
While the salmon cooks, pour the reserved marinade into a small skillet and simmer over low heat, stirring, until it thickens slightly, about 1 to 1 1/2 minutes.
Brush the reduced sauce over the cooked salmon, then sprinkle with toasted sesame seeds and chopped scallion. Serve the salmon with the roasted vegetables.