Weißherbst, literally 'white autumn', is a special German style of rosé. Basically, it involves red grapes done in white wine style, but the grapes can only be of one variety. The grapes do also have to be sourced from the same area. In the case of the Salwey RS wines - Reserve Salwey - they do actually come from the same vineyard and are of late harvest quality.
The Salwey Weißherbst comes from sun-kissed Baden, and it has been matured in oak barrels. I did not tell that to my friends who tasted it blind, which resulted in an interesting description of the wine's bouquet - that it was a rosé they could clearly see, of course.