Preheat your oven to 400°F and line a large baking sheet with parchment paper for easy cleanup.
Dice the red potatoes into small 1/2-inch cubes and place them on one side of the baking sheet, seasoning with a pinch of sea salt and black pepper.
Roast the potatoes for 10 minutes to give them a head start on getting crispy.
While the potatoes roast, whisk together the Dijon mustard, lemon juice, dried parsley, dried dill, and garlic powder in a small bowl.
Pat the salmon fillet dry with a paper towel and brush the mustard herb mixture evenly over the top of the fish.
Remove the baking sheet from the oven, move the potatoes to one side, and place the salmon fillet and broccoli florets on the other side.
Return the sheet to the oven and roast for an additional 12-15 minutes until the salmon is opaque and flakes easily with a fork.
While the main components roast, prepare the salad by tossing the spring mix with sliced celery, halved cherry tomatoes, and sliced kalamata olives.
Plate the herb-crusted salmon alongside the roasted potatoes and broccoli, serving the fresh garden salad on the side.