You want about 2 pounds of hard vegetables total, cut into 1" cubes roughly. I've used acorn squash, rutabagas, and sweet potatoes in various combinations with the vegetables listed above.
Mix them all with a bit of oil and/or melted butter. Put them in a roasting pan.
I've cooked them two different ways, depending on what else I was serving. However you cook them, stir them now and then and roast until at least soft, and browned a bit is even better.
If you're in a hurry, roast them at 500 degrees for at least 30 minutes.
If you're not in a hurry, roast them at 425 for up to an hour.
The timing is rough. You have to just watch them, stir them, stick a fork in them now and then and see how they're doing.