Preheat oven to 375 F.
In a medium bowl, whisk together the chopped parsley, lemon juice, and olive oil.
Chop the carrots, parsnips, rutabaga, and beets into 1-inch cubes, then slice the fennel and onion into large chunks. Place in a large bowl and toss with the lemon-parsley sauce and salt. Spread the vegetables onto one large or two medium rimmed sheet pans, ensuring they don't overlap.
Bake for 45 minutes to 1 hour, or until outside of vegetables is crisp and they are easily pierced with a fork.
Remove from oven and serve warm!