Prepare the vegetables by washing and cutting them into uniform sizes.
Heat the vegetable oil in a large skillet or wok over medium-high heat.
Add the garlic and ginger, sauté for about 30 seconds until fragrant.
Add the cauliflower and broccoli florets, stir-frying for about 5 minutes.
Incorporate the bell pepper and sauté for an additional 2-3 minutes.
Pour in the soy sauce and drizzle with sesame oil, tossing to coat evenly.
Sprinkle red pepper flakes if desired, adjusting heat according to taste.
Cook for an additional minute, stirring frequently, then remove from heat and serve immediately.