The text does say that dapsone has been involved in a case report of an interaction (together with pyrimethamine and ethanol), but it doesn't explain what happened or how it would affect roflumilast. So there's no clear effect to describe for roflumilast and dapsone taken together.
These medicines are often taken together with some care. Your doctor may change a dose, space them apart or check on you more often. Make sure your doctor and pharmacist know you take both.