This is an open pollinated 1999 seedling of Henry Hudson that flowered while still in the sunroom. In addition, another bud is forming while this one was opening. In my experience, most rugosas have taken several years before they flower. The flower is very fragrant. Now, to see what type of plant this seedling forms and whether it is fertile.
The mother, Henry Hudson, is an open pollinated seedling of Schneezwerg. Suzanne Verrier in her book "Rosa Rugosa" lists the parents of Schneezwerg as probably R. rugosa X R. bracteata. Others report the parantage as possibly R. rugosa X Polyantha hybrid.