Heat your oven to 425 degrees.
Chop the asparagus into 1" pieces, discarding the last 1/2" of the stems. Chop the cauliflower into bite sized pieces. Cut the potatoes into 1/2" chunks, and cut the brussels sprouts in half.
Place all veggies on 2 baking dishes to ensure there's no overlap in the veggies, and roast for 40 minutes, stirring half way through.
Make the sauce: dice the garlic, and mix in a small bowl with the veganaise, parsley, and lemon juice. Stir well, and set aside.
Remove the veggies from the pan, let cool for a few minutes, and stir in the quinoa. Then add the veganaise sauce, stirring well.
Serve immediately. The veggies will last for a few days in the fridge, and are great as cold leftovers too!