Preheat your oven to 400°F and line a large sheet pan with parchment paper for easy cleanup.
Peel and cube the sweet potato into half-inch pieces, then toss them on the pan with half of the olive oil and a pinch of salt.
Roast the sweet potatoes for 10 minutes to give them a head start since they take longer than the other ingredients.
While the potatoes roast, trim the woody ends off the asparagus and slice the red bell pepper into strips.
Remove the pan from the oven, move the potatoes to one side, and add the asparagus and bell peppers to the other side.
Place the salmon fillet in the center of the pan.
Whisk together the remaining olive oil, lemon juice, minced garlic, and oregano in a small bowl.
Drizzle the lemon-herb mixture over the salmon and all of the vegetables, then season with the remaining salt and pepper.
Return the pan to the oven and roast for 12 to 15 minutes, or until the salmon is opaque and flakes easily with a fork.