Last week, the conclusions of my highly scientific study proved that roasting vegetables below 400° F is, in most cases, suboptimal.
Unless you're going for a very low and slow roast (200° and 250° F for upwards of an hour, so that your vegetables are silken through and through), the goal is to cook the outsides before the insides, so that you get crispy outer edges before inners get mushy—and this takes place at higher temperatures.
When we asked the audience their go-to roasting number, 48% said 400° F.
But the recipes for commonly roasted vegetables on our site suggest that we should have listed 425° F as an option, too. It may be the most common roasting temperature (though, as you'll see below, there are a few recipes that thwart the rule and go for 375° or 500° F).
So with all this variation—in recipe method and opinion—what's a person to do?
Consider your vegetables and group like with like.
Vegetables are individuals. Treat them as such. ChefSteps recommends sorting your lot: Group squash, roots, tubers, and alliums together (on the same baking sheet, if you want!). They require a longer cooking time (ChefSteps recommends 45 minutes). Brassicas (cauliflower, brussels sprouts, broccoli) and mushrooms can be baking sheet buddies (they need only about 25 minutes). For both groups, ChefSteps suggests—you guessed it—425° F.
Cut the vegetable pieces so that they're more or less the same size.
Otherwise, the 1/2-inch cubes will be done long before the 2-inch ones.
Don't crowd the pan.
On a too-full baking sheet, your vegetables will steam each other, resulting in sog rather than crisp.
Use enough oil.
The oil moistens the vegetables (to prevent them from sticking to the pan) and it helps to transfer the heat from the baking sheet to the food.
Flip halfway through.
Give both sides of the pieces a chance to interact with the direct heat of the baking sheet.
A (former) student of English, a lover of raisins, a user of comma splices. My spirit animal is an eggplant. I'm probably the person who picked all of the cookie dough out of the cookie dough ice cream. For that, I'm sorry.