Preheat oven to 375 degrees. Line a baking sheet with parchment paper.
Spread broccoli in an even layer on a baking sheet and add a dash of salt and pepper, if desired.
Bake for 15-20 minutes until fork tender and lightly browned on edges.
Cheese Sauce:
While broccoli roasts prepare cheese sauce. Combine potatoes, carrots, garlic and non dairy milk in a small sauce pan. Bring to a boil, reduce heat and simmer until potatoes are easily pierced with fork.
Allow to cool a couple of minutes and carefully transfer to a blender. Add nutritional yeast, mustard and salt. Blend until smooth, stopping to scrape down sides with a rubber spatula as needed.
Taste and adjust seasonings to your liking. Return to pan to warm if needed.
Pour over roasted broccoli and serve immediately.
Notes
As the sauce cools, it will thicken. Simply warm on the stove and the sauce will thin and become more liquid.
Leftover sauce be stored in the fridge. It will thicken considerable. Simply warm and sauce will thin.