There is an image of this cultivar on the Hosta Library. From the photo on the HL website, it appears to be a small size hosta with light green leaves and a misting of creamy white specks. This non-registered cultivar was originated in Japan.

W. George Schmid (1991) describes a Rasha leaf as one that is a "Uniquely contorted leaf with an unevenly knotty and knurled surface texture". 

Mikiko Lockwood in an article on The Hosta Library titled, A Little About Japanese Hosta Terms defines the term iwa as rock, Iwa Gibōshi or H. longipes.