Preheat the oven to 375 degrees F.

Melt butter in small saucepan over medium heat and add flour. Allow to cook, stirring frequently, for 2 minutes.

Add milk, whisking constantly until just reaching a simmer. Stir in cheese and season with salt and pepper.

Place naan on baking sheet and top generously with cheese sauce, leaving a little crust uncovered.

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.

Remove from oven and top with fresh rosemary.