I do this for holidays and this year I perfected it. I think the most important part is to use a shiny roasting pan, not a non-stick sort, and really blast the heat at the end to crisp/brown things up.

Ingredients:

Root veggies and/or winter squashes like: turnips, rutabagas, celery root
Squashes: Butternut, kombuka, acorn, etc.
Carbier alternatives: Yams, potatoes, parsnips

Oil, olive is good
Salt (coarse kosher salt works for me)
2 heads (not cloves, heads) of garlic
Many springs of rosemary and/or thyme, fresh. LOTS!

Select some low carb root vegetables. Clean and peel if necessary. Cut them into pieces that'll finish cooking around the same time. Note: Denser veggies should probably be cut smaller than less dense ones. For instance, celery root takes longer than turnip (I think).

Throw them into your roasting pan, try not to put too many in. Maybe a little more than what'll go in one layer on the bottom of the pan. The veggies are best that are in contact with the metal.

Pour olive oil over the veggies and toss so that everything gets coated. Sprinkle on salt and toss more.

Whack the heads of garlic with something hard to make the cloves separate. Then crush each clove with a hard object. No need to completely peel, just crush the clove and throw it into the pan with a little peel attached, people can just pick them out. Pull off some of the rosemary leaves, or throw in clusters of them. Doesn't matter too much. Same with the thyme. Toss well.

Put into a 375' oven. Pull out the pan and toss every 30 minutes until the veggies start to get soft. Just before they've reached the perfect doneness turn up the heat to 500' and brown them nicely.

To serve just tell everyone to discard the garlic skins. Add more salt if needed.

This smells absolutely heavenly. My guests LOVED this dish.