Cut vegetables into evenly sized pieces so that they cook at the same rate. I typically cut broccoli and cauliflower into medium florets, carrots and parsnips (peeled) into 1/2-inch rounds sliced on the bias, and Brussels sprouts in half. Divide the vegetables among 2 large baking sheets and coat with olive oil and 1.5 tsp. kosher salt. Spread the vegetables out so that they form an even layer and roast them in a pre-heated 425° oven for 20-25 minutes or until lightly browned. See TIP A for additional vegetable roasting tips.
TIP A: Roasting brings out a depth of color, texture, and flavor in vegetables. So, never roast so long that you compromise any of these characteristics. And, never under-roast...because, well...what was the point of even putting them in the oven. It's not hard to get the roasting time right if you pay attention to all 3 indicators. First, color: look for the edges of most pieces to turn brown and the interior to take-on its most vibrant natural hue (green, orange, yellow, etc.). Don't allow the vegetables to transition to a muddy color. This is an indication that they're over-done. Second, texture: you want the vegetables to resist ever-so-slightly when you poke them with a fork, and this resistance should feel even throughout. The fork should not slip in (over-done) or require significant pressure (under-done). Lastly, flavor: there's no other way to test flavor than to pop a piece in your mouth. The flavor should be slightly butter-y/caramel-y, how you imagine the vegetable's concentrate would taste.