There is an image of this cultivar on the Hosta Library. From the photo on the HL website, it appears to be a very slow growing, miniature size hosta with dark green leaves. The petioles are covered in reddish dots which extend up into the base of the leaf blade. This non-registered cultivar was originated in Japan by Kichigoro Suzuki. 

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.