Preheat the oven to 425°F.
In a large bowl, toss the asparagus, shallot, balsamic vinegar, dried basil, dried tarragon, garlic powder, white pepper, and kosher salt (if using).
Add the mixture to a 9x13-inch casserole dish, spreading it out evenly. Roast for 10 to 15 minutes, or until the asparagus is fork-tender but not limp.
While the asparagus and shallot are roasting, boil the vegetable broth and white wine in a small pot on the stove.
At the end of the asparagus and shallot roasting time, remove the casserole dish from the oven.
Add the couscous, peas, and spinach to the casserole dish. Carefully pour the broth-and-wine mixture on top. Press down gently with the back of a spoon to submerge the couscous and vegetables as much as possible. Cover the casserole dish with aluminum foil and return it to the oven for 20 to 25 minutes, or until the couscous is soft and has absorbed the liquid.
Remove the casserole dish from the oven and stir well. If any couscous remains uncooked (this may happen around the edges), add additional broth or water 1 tablespoon at a time, stir well, and return the casserole dish to the oven for 1 to 2 more minutes, until the liquid is absorbed. Once the couscous is completely cooked, remove the dish from the oven, add 1 teaspoon of lemon juice, stir, and taste. If you prefer more lemon flavor, add more fresh lemon juice in increments, tasting as you go, to avoid overpowering the other flavors. If desired, garnish with vegan Parmesan, nutritional yeast, fresh basil leaves, lemon zest, freshly cracked black pepper, and/or a pinch of flaky sea salt. Serve warm.