You could easily substitute any leafy green for the bok choy such as spinach, kale or escarole. I really like this brand of vegan sausage called Field Roast because they are made with vital wheat gluten which is low in fat and high in protein.
You’ll want to put your pasta water on to boil, and put your oven on to roast the cauliflower as your first steps.
You could combine chopped cauliflower, escarole and sausages in one pan on stove if you are in a hurry. Browning the sausage separately and roasting the cauliflower are extra steps that will add flavor, but cost you time. It depends on your energy budget!