If you have a friend who knows how to turn out a pan of perfectly roasted vegetables, that is a friend to stick close to and learn from.
My friend Shelley fits the description perfectly. She's awfully generous about having us over to dinner. She doesn't sweat bullets over the food and frequently the vegetables are simply placed in a pan in the oven to cook themselves.
But oh, they are divine. Many times I tried to duplicate them without much success. Then it occurred to me that while my roasted vegetables seemed to come out of the oven mostly dry and lifeless, it might be because I was cooking them on a baking sheet rather than in a casserole. I tried roasting them in a tall-sided Pyrex casserole and finally achieved a very different result: roasted vegetables that were tender and moist, the way we've been enjoying them for so many years at Shelley's.
It seems that the extra inch or two of glass separating the vegetables from the scorching heat of the oven makes all the difference. So my first recommendation is, if you want tender, moist roasted vegetables do it in a casserole, not on a baking sheet. (There is another school of thought about slow-roasting on a baking sheet at much lower temperatures, but that's a story for another time.)
These are vegetables to be approached casually. Preheat your oven to 350 degrees. Then peel two parsnips and two carrots. Cut them on a sharp angle into pieces about 3/8-inch thick. Next, cut an onion into eight wedges, then carefully remove the skin and the rough parts from both ends, but leaving the wedges intact. Trim the top off a fennel bulb and slice it from top to bottom into 1/4-inch pieces. Smash but don't peel two garlic cloves.
Place all the vegetables in a large bowl and toss with 2 tablespoons extra-vigin olive oil and 1 tablespoon fresh thyme leaves (a teaspoon or so of dried thyme works as well) and season with coarse salt. Toss everything together, then turn out the vegetables into a rectangular Pyrex casserole. Drizzle a tablespoon or two of Vermouth or dry white wine over the vegetables, then place in the oven and bake, uncovered, for about 45 minutes, stirring the vegetables once or twice.
Don't be afraid to pour in some more Vermouth or wine if the vegetables become dry. They are done when cooked through and tender to your taste. They would be perfect next to a roasted chicken or just about any kind of grilled meat.