Preheat oven to 425

Combine broccoli, 1 1/2 tablespoons oil, 1/4 teaspoon kosher salt, and crushed red pepper on a baking sheet; spread in a single layer. Bake at 425°F for 20 to 25 minutes or until broccoli is charred and browned in spots, stirring after 15 minutes.

Bring a large saucepan filled with water and remaining 2 teaspoons kosher salt to a boil. Add pasta, and cook 7 to 8 minutes or until al dente. Drain in a colander over a bowl, reserving 3/4 cup cooking liquid

Heat remaining 1 1/2 tablespoons oil and garlic in a large skillet over medium-low. Cook 2 minutes or until garlic is golden, stirring occasionally. Sprinkle flour over pan; cook 30 seconds, stirring constantly. Gradually add reserved 3/4 cup pasta cooking liquid and milk to pan, stirring constantly with a whisk. Stir in feta; cook 3 minutes or until feta begins to melt and sauce is slightly thickened.

Add broccoli, pasta, and lemon juice, and pepper to sauce; toss.