1. Preheat oven to 375°F.
2. Melt butter in small saucepan over medium heat and add flour. Allow to cook, stirring frequently, for 2 minutes.
3. Add milk, whisking constantly until just reaching simmer. Stir in cheese and season with salt and pepper.
4. Place naan on baking sheet and top generously with cheese sauce, leaving a little crust uncovered.
5. Top with potato slices, leaving open place in center for egg, followed by sausage. Place egg in center and bake until lightly browned and warmed through, 8 to 10 minutes.
6. Remove from oven and top with fresh rosemary.