I was telling Andy about my experience and wondering why the cook hadn't bothered to roast the vegetables properly. Andy commented that the kind of restaurant that this was—one of the new "fast food"-type places that serve fresh, cheaply priced fare, presented in a mildly artful way on a plate as opposed to being handed to you in a paper wrapper—didn't really have the money to train teenagers how to roast vegetables properly. (To be fair, what I think he actually said was that I couldn't expect them to train teenagers to roast vegetables to my standards). I grudgingly agreed. But if I were Queen of the Universe, a teenager wouldn't have to be taught how to roast vegetables at their first job. They should already know how. They eat don't they? Shouldn't they be able to feed themselves?
Okay, so expecting a teenager to know how to roast vegetables may be a bit unreasonable. It may even be presumptuous to say that roasting a vegetable is a simple thing. We really do live in a society where basic cooking is not a universal skill. From the reactions that I get when I serve a plain roasted vegetable to someone ("What did you do to this? It is so good!"), I think I can safely conclude that many people do not know how to roast vegetables and are not doing it at home. This is unfortunate because a vegetable that has been roasted correctly is easy to like—it's flavor is concentrated and sweet. Roasted vegetables are also generally not mushy or water-logged. Mushy, overcooked vegetables are a major reason that so many people think they don't like vegetables. If you are trying to teach your kids to eat vegetables, try serving them roasted vegetables.
The basic method for roasting a vegetable is to toss it with enough oil to lightly coat, season with salt and pepper, spread on a baking sheet and roast in a hot oven until tender and caramelized. This is really all there is to it, but for those who are not so comfortable in the kitchen, this could be a daunting task. All kinds of questions come up in those simple instructions...what size do you cut the vegetable? (could it be roasted whole?)...how much oil?...how much salt and pepper?...what temperature?...how long?...
When I am teaching someone how to cook something, I always tell them to think about the goal. What exactly is it that they are trying to achieve? With roasted vegetables, the goal is a tender vegetable (degree of tenderness will vary depending on the vegetable, but generally it should be the degree of tenderness preferred by you) that has a golden brown (sometimes crispy) exterior. So, when you are getting ready to roast a vegetable, you need to think about what needs to be done to the vegetable during the cooking process to reach this goal.
Vegetables can be cut in pretty much any size for roasting—large dramatic pieces for a roasted vegetable platter for a buffet, 1/4- to 1/3-inch thick slices for topping a pizza, 1 to 2-inch chunks for a simple vegetable side dish. Really, the sky is the limit. The only rule is that you cut everything that is going into the oven at the same time, in the same pan, as close to the same size as you can manage. This way the vegetables will all be cooked at the same time.
But even this isn't so straight forward. The density of the vegetables that you are roasting needs to be considered. A one inch chunk of carrot will take much longer to roast than a one inch cauliflower floret for example. The solution to this is to roast dense vegetables (root vegetables, for the most part) on separate pans from things that will roast more quickly (cauliflower, Brussels sprouts, asparagus, peppers, mushrooms, etc.)--or add these less dense vegetables to the pan with the denser vegetables when they are half cooked. Another option when faced with vegetables that will roast at different rates is to cut them in different sized pieces. You'll notice in the pictures below that I have paired carrots and cauliflower. The carrots are cut into thin slices and the cauliflower has been cut into 1-inch florets. This way they will take the same amount of time to roast.
After you have chosen your vegetables and cut them up, they need to be coated with oil. The oil protects them from drying out on the outside and also encourages them to brown. With this in mind, you will need just enough oil to create a nice light coating on all of the vegetable surfaces. Too much oil, and the vegetables will be greasy and possibly soggy.
To coat the vegetables in oil, place them in a large bowl and drizzle some oil over them. Toss to coat. Add more oil if they are not evenly coated. If you have added too much oil and there is oil pooling in the bottom of the bowl, that's OK, just lift the vegetables out of the bowl to transfer them to the pan (rather than dumping the contents of the bowl—excess oil included—onto the pan). I know that chefs are seen on TV spreading vegetables on a pan and then drizzling the oil directly over them. This does save washing a bowl, but unless you have been roasting vegetables a long time and have a sense of how much oil you need for the vegetable in question, you could end up with too much oil in the pan. Finally, as far as choice of oil is concerned, I generally use an inexpensive, all-purpose, extra virgin olive oil for roasting vegetables.
Before transferring the vegetables to the pan, season them with salt and pepper. Since most vegetables are edible raw, seasoning the vegetables to taste is an easy thing to do: just taste one. You could also add a favorite spice (cumin, fennel, coriander, chipotle chili powder, etc.) or some herb sprigs or leaves (something sturdy like thyme, sage, rosemary, winter savory), if you like.
Choose a pan size that will hold the vegetables in a snug single layer. If the vegetables are spread out with lots of space in between them, they will tend to burn before they are tender. If they are too crowded and are piled on top of one another, they will steam and only the ones on top will brown. Worse yet, the ones on the bottom will not have a chance to form a crust and when they are tender will likely fall apart. I think sheet pans are the best pans to roast vegetables in, but I also use shallow gratins.
Now that the vegetables are cut, oiled, seasoned and in the pan, at what temperature should they be roasted? Generally somewhere in the 375° to 475° range. Exactly where in this range depends on a number of things. Remember that the goal is tender interior and a crisp or golden exterior. These two things need to happen at the same time. A vegetable that is particularly dense (again, a carrot, for example) or one that is cut into very large pieces will brown before it is tender if put into a really hot oven. Conversely, one that is less dense or is cut in very small pieces will get tender long before it begins to caramelize if put in an oven set too low.
Frequently a recipe will tell you to "stir" the vegetables occasionally to insure even browning. The biggest pitfall here is stirring too soon and too often. If stirred too soon, the exterior of the vegetable will not have had time to harden or "seal" and stirring will tear the vegetables up since they are beginning to soften from the outside in. Also, if stirred too often, the vegetables won't brown very well. I usually stir vegetables once—and it isn't really "stirring". I use a wide spatula or pancake turner to scrape the vegetables off of the pan and flip them over. I usually wait to do this until the vegetables are about half cooked.
Finally, to test the vegetables for doneness, taste one. Or test for tenderness with the tip of a paring knife—the knife should slide in and out without encountering resistance or a change in texture as it passes from the outer to the inner portion of the vegetable.
As far as how long it will take to roast the vegetables, the standard answer is "until they are done". As you can now guess, this too depends on size and density of the vegetables. But, to give you some very general parameters, when I am roasting vegetables that require a very hot oven (475° or so), I start checking them at 20 minutes. For vegetables that roast at a medium temperature (375° to 400°), I begin checking at 40 minutes and realize that they may take as long as an hour. These are guidelines for a still or standard oven. If you are roasting in a convection oven, the times will be less.
One last thing, all of these tips and pointers are meant to just provide some baseline guidance and will only be helpful to you if you are willing to be engaged in the process. For example, ovens vary widely in how they cook. If you are roasting something and it's browning too fast, then turn the oven down in 25° increments. If you roast something and it's tender, but not browned, make a mental note to cook it at a higher temperature next time. Vegetables themselves change throughout the growing season in moisture and sugar content—they will cook a bit differently each time.
Also, I have limited my discussion to basic guidelines for a basic roasting method. There will be times when a vegetable needs to be covered during the roasting process. Sometimes vegetables can be roasted whole (eggplant, peppers, winter squash, corn in the husk...). The guidelines I've given are clearly not exhaustive. But for the novice, they are a good start. They are meant to help you make decisions about how to proceed when confronted with a vague recipe, or when you have no recipe at all.
Who knew there could be much to say about the simple process of roasting a vegetable? Perhaps I should have reconsidered calling this post a "mini" tutorial....
The cauliflower and carrots cut and in the bowl with salt, pepper and a drizzle of olive oil. Note that the carrots are in smaller pieces than the cauliflower:
Spread on the sheet pan in a "snug single layer" prior to roasting:
After roasting for about 20 minutes at 475° (they were "stirred" once):
Added to a pasta with Walnut-Parsley Pesto for dinner: