Scrub lemon thoroughly. Zest the entire lemon into a small bowl; juice the lemon into another small bowl.

Place a heavy medium sized saucepan over medium heat. Add the bacon to the pan and cook, stirring occasionally, until browned and fat renders. Remove to a plate and reserve.

Take the pan off the heat and add the red pepper flakes and rosemary; stir until fragrant. Add the garlic and stir to combine. Return the pan to the stove, add the beans, broth, roasted peppers, and lemon zest. Bring to a simmer and cook, stirring occasionally, until the broth thickens and flavors combine; about 15 minutes. Add half the lemon juice and black pepper to taste; stir to combine and taste, adding more lemon juice and salt, if necessary. Drizzle the olive oil over the beans and top with reserved bacon.

Serve at once.