Preheat oven to 375 degrees F.
Line a large baking sheet with parchment paper or grease a 9 x 13 inch baking pan.
Dice the parsnips, yukon potatoes, and sweet potatoes into 1/2-inch cubes, and place everything in a large mixing bowl.
Add diced onions and garlic to the root vegetables.
Add the olive oil, thyme, sea salt, and any other dried herbs you want to the vegetable blend and mix everything together.
After blending the root vegetables, oil, and spices together, pour out the contents onto a baking sheet or baking pan.
Bake in the oven for a total of 40-45 minutes, stirring the vegetables once in between. Once the vegetables are browned, they are ready to take out of the oven.
Top with a bit of parmesan cheese, parsley or any garnishes. This is completely optional.