Preheat oven to 400 F and line a large baking sheet with parchment paper.
Place butternut squash, sweet potato and brussels sprouts on baking sheet and spray with a little cooking spray then sprinkle crushed red pepper flakes over vegetables and salt and pepper as desired.
Roast vegetables 30 minutes stirring once every 10 minutes.
While vegetables are roasting, whisk together the mustard and oil in a small bowl.
Remove vegetables from oven, toss in the dressing and serve immediately. Keep leftovers in the refrigerator up to one week.
Notes
Save yourself some prep time and purchase shaved Brussels sprouts at the grocery store. You could also use the food processor to give them a quick pulse to chop. I also like this veggie chopper from Amazon.
After rinsing and chopping your Brussels sprouts be sure to pat them dry to absorb the excess moisture. This helps them crisp up in the oven.
Space the chopped vegetables out to ensure they roast evenly and caramelize on the outside.