Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper.
Peel and cube the sweet potato into half-inch pieces. Toss them on the baking sheet with half of the olive oil, a pinch of sea salt, and black pepper.
Roast the sweet potatoes for 10 minutes to give them a head start.
While potatoes roast, pat the salmon dry. In a small bowl, mix the remaining olive oil, lemon juice, dried dill, and dried parsley.
Remove the tray from the oven. Move the potatoes to one side and place the salmon fillet and broccoli florets on the other side.
Brush the herb mixture over the salmon and lightly season the broccoli with any remaining oil and salt.
Return the tray to the oven and roast for 12-15 minutes, or until the salmon flakes easily with a fork and the broccoli is tender-crisp.
Warm the pre-cooked lentils in a small saucepan over low heat for 2 minutes.
To serve, spread the lentils on a plate, top with the roasted sweet potatoes and broccoli, place the salmon on top, and finish with a dollop of Greek yogurt.