Toss the squash with a tablespoon of oil and season with salt and pepper. Spread on a baking sheet and roast for 15 minutes.
Remove from the oven and push the squash to the side to make room for the salmon. Lay a bit of aluminum foil on the side where you are going to roast the salmon. Season the salmon with salt and pepper and a little drizzle of olive oil. Roast until cooked through about 5-10 minutes.
Remove from the oven.
In a small lidded jar combine the 4 tablespoons of olive oil, ½ teaspoon salt, ¼ teaspoon pepper, cider vinegar, maple syrup and mustard. Close the jar and shake to combine. Reserve 2 tablespoons of the dressing.
In a large bowl combine the arugula, cabbage, and squash. Flake the salmon into the bowl. Pour over the dressing and toss gently to combine.
Serve with the reserved dressing sprinkled over the top.