Preheat oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper.
Remove any damaged outer leaves from the cabbage and cut the head into 1-inch thick rounds or wedges, keeping the core intact to hold pieces together.
In a small bowl, whisk together the olive oil, minced garlic, salt, black pepper, and red pepper flakes.
Place cabbage slices on the prepared baking sheet in a single layer and brush both sides generously with the garlic oil mixture.
Roast in the center of the oven for 20 to 25 minutes, flipping halfway through, until the cabbage is tender and the edges are browned and crispy.
Drizzle with fresh lemon juice before serving.