This is one of those cases where there are two hostas with the same name. One is registered and, therefore, the "official" version of H. 'Roundabout' while the other is a non-registered plant and needs to be renamed to avoid further confusion.
 

In 1988, Robert Savory of Savory's Gardens in Minnesota registered this cross of H. 'Rough Waters' × a seedling which forms a dense, medium size (17 inches high by 3 feet wide) clump. The leaves are slightly cupped and moderately corrugated. Lilac colored flowers bloom starting in mid-June.

According to The Hostapedia by Mark Zilis (2009), "...leaves of 'Roundabout' are nearly circular and are also cupped."

Similar cultivars include H. 'Pearl Lake'.

According to The Genus HOSTA by W. George Schmid (1991) , "Plant described here is sold under the same name Savory registered for another plant...Source unknown." It is a medium size plant about 18 inches high by 30 inches wide with yellow foliage. It bears white, bell shape flowers in July followed by fertile seeds.