Sclerocactus whipplei 'rosei'

Sclerocactus whipplei is known to have yellow flowers. This pink-flowering plant makes it very confusing, but if you look closely you see the distinct upward-pointing flat white spine, characteristic to the species. It is well seen on original 1856 illsutration by Paulus Roetter stored in National Museum of Natural History  (click the link to see).
The pictured plant is probably as small as those plants can flower - very encouraging sight for those who grow  them from seed.