In a food processor or blender, add the drained chickpeas, broth, olive oil, nutritional yeast, soy sauce, sage, thyme, rosemary, onion powder and garlic powder and blend or process until smooth.
Transfer the blended mixture to a large mixing bowl, getting all the last bits with a spatula.
Add the vital wheat gluten and start to mix it into the wet ingredients with a spatula or spoon, then use your hands and mix until it starts to come together. Sprinkle a little vital wheat gluten on a clean surface, transfer the mixture to the surface and knead about 10 times. Carefully shape it into a loaf.
Get out a large pot with a steamer basket (flat bottom preferred, see Notes if you don't have steamer basket.) Place the loaf on the steamer basket with 3 cups of broth on the bottom for steaming.
Cover, bring to a boil, then reduce the heat so it’s simmering but not boiling too hard. Steam for 1 hour, and make sure to add more broth if it evaporates too soon. You can pour some additional broth over the roast halfway through.
Remove the pot from heat and open the lid so the loaf can cool for a few minutes.
To brown the outside, heat a large skillet over medium-high heat (you could use the same pot you used for steaming). Add the vegan butter and let it melt, then add the soy sauce and stir. Place the cooked loaf in the pan and let it brown on all sides.
Place on a cutting board or serving platter, sprinkle with herbs and slice thinly. Serve immediately with vegan gravy and mashed potatoes.