I got this one Chef.....
It sounds like you enjoy "roasted veggies" but it sounds as if you're "steaming" them in your cooking technique. Many people think that placing a potato wrapped in tinfoil, in the oven is a "baked" potato, nope, it's a "steamed" potato, en papillote comes to mind. You're basically doing the same thing when you use the Dutch oven, your veggies are steaming in their own juices.
Take those same veggies and toss them in a bowl with a bit of olive oil, thyme, rosemary, season with salt and pepper, toss to coat. Dump the veggies on a cookie sheet and throw into the oven 375-400 for about 30-45 minutes. The size of your cuts will determine how long to "roast" them in the oven. This should work on your grill, just make sure you close the grill cover. They are done when fork tender.
If you pace a bit of tinfoil on the bottom of your cookie sheet first theres no cookie sheet clean-up.