It is important to start with a hot oven. Roasting occurs above 400 degrees, as opposed to baking which is usually somewhere between 300 and 400. When you roast at a high temp (in this case 425 degrees) you are less likely to steam the veggies and salmon and it cooks them more quickly. I like the way the salmon is just medium-well and the green beans and fennel are crisp-tender.