Preheat your oven to 375F, and prepare a baking sheet by lining it with parchment paper or a silicone mat.
Toss the potatoes, onion, mushrooms, carrot, celery, olive oil, salt and pepper together in a mixing bowl.
Spread the contents out over the baking sheet, into one layer. Bake for 20 minutes.
Put the quinoa and vegetable broth into a large sauce pan, cover with lid and heat to a boil at medium heat. Once boiling, reduce to low-medium heat, simmer for 18-20 minutes.
Fluff the quinoa with a wooden spoon, once cooked. Stir the nutritional yeast and roasted vegetables into the quinoa, along with the Italian Seasoning.
Season with salt & pepper to taste, and adjust the oven to 350F.
Take the lining off of the baking sheet and lay out a large square of foil on a flat counter top or table.
In a blender, puree the vegetable broth, mushrooms, garlic, liquid aminos and olive oil together until completely smooth.
Sift together the vital wheat gluten, chickpea flour, nutritional yeast, poultry seasoning and black pepper, in a large mixing bowl.
Pour the wet mixture into the dry, stir together, then knead for 1 minute.
Roll the seitan out into a square on the foil, about 1/2" thick if possible. It may be thicker than that in spots.
Pile the stuffing into a wide line the center of the seitan, and press it down slightly to compact it. Carefully fold the seitan over the stuffing and pinch together the ends and seam.
Using the foil, turn the roast into a huge "Candy" by rolling it length-wise then grabbing the loose foil and twisting it until tight. Be careful not to tear the foil.
Place your roast onto the baking sheet and bake it for 50-55 minutes, turning it 90º every 15 minutes. The roast should be slightly firm.
Take it out of the oven and unwrap the foil, halfway, making sure not to tear the roast. Bake it for an additional 10 minutes, or until golden brown on top. Let cool for 15 minutes before serving.
Serve with a side of gravy or vegetable broth, to add more moisture.