In a medium bowl, combine water, soy sauce, brown sugar, garlic, ginger, and oil.
Place salmon in a tupperware or plastic baggie and add 1/4 cup of the sauce. Let it marinate for at least 20 minutes, up to overnight.
Preheat the oven to 400 degrees F.
Add chopped veggies to a bowl along with 1/4 cup of the sauce. Arrange on a greased or parchment/foil lined baking sheet.
Bake in the preheated oven for 15 minutes. Make room for the salmon on the baking sheet and arrange the salmon among the vegetables. Bake an additional 10-15 minutes, until the veggies are roasted and the salmon flakes easily.
Meanwhile, add the rest of the sauce to a small saucepan over medium heat.
Once it is simmering, add the cornstarch/water mixture and cook until thickened, just a couple of minutes.
Brush the teriyaki sauce over the cooked salmon and serve sprinkled with sesame seeds.