Vegetable Broth

3 In a large stockpot with a lid (be sure to use an oven-safe one if taking the optional step to roast), combine the vegetables.
0 Optional step to roast (see note): Preheat oven to 400°F. Drizzle oil over the vegetables; toss to coat. Sprinkle with 1/2 teaspoon kosher salt. Roast vegetables until tender and golden, stirring occasionally, about 40 minutes. Remove from oven.
1 Pour water over the vegetables (if you roasted it first, scrape up any browned bits on the bottom of the pan).
4 Bring the water to a boil. Reduce heat, cover and simmer 30 minutes. Taste the broth. If you would like to season it lightly with salt, you can add some now. (If you roasted the vegetables keep in mind that they are already lightly seasoned.) Seasoning the broth at this stage is optional - you can always season it later when you use it in a recipe. 
5 Strain broth through a sieve and let cool completely. 
2 Use immediately, refrigerate for several days, or freeze.