Preheat the oven to 400 degrees F (200 degrees C). Line a baking sheet with parchment paper.

Place broccoli, onion, garlic, and olive oil in a large bowl and toss to coat evenly. Place on the prepared baking sheet in a single layer.

Roast vegetables until soft, 30 to 35 minutes, stirring every 10 minutes. Remove from oven. Chop 1/4 cup of broccoli florets; set aside for garnish.

Combine remaining vegetables with vegetable broth, cream cheese, and lemon pepper in a high-powered blender or food processor in batches. Puree soup until smooth.

Pour soup into a saucepan over medium-low heat until warmed through, about 5 minutes. Season with additional lemon pepper to taste. Ladle into bowls. Garnish with reserved chopped broccoli and crushed red pepper.