Preheat oven to 450 degrees. Line a baking sheet with parchment paper. Chop the potatoes and radishes into quarters. Peel and large chop the red onion. Chop the broccoli into florets
Add the potatoes to the baking sheet. Toss with ½ tablespoon olive oil and season with salt and pepper. Roast in preheated oven until tender, about 15 minutes. Remove from oven.
While the potatoes are in the oven, in a large bowl, toss the radish, red onion and broccoli florets with remaining tablespoon of olive oil and season with salt and pepper. Prepare salmon. Pat dry with a paper towel. Season on both sides with salt and pepper.
Toss the radish, red onion and broccoli with the cooked potatoes on the baking sheet. Push the veggies towards the sides of the baking sheet, making room for the salmon fillet.
Position salmon (skin side down) in the middle of the veggies. Spread 2 tablespoons of the sun-dried tomato aioli over salmon. Return the baking sheet to the oven until all of the vegetables are fork-tender and the salmon is no longer translucent and the desired level of doneness is reached, 15 to 20 minutes.
Remove from oven. Serve alongside extra aioli and fresh lemon.