Here is another online source for the Roos:
http://predecimal.nf/roo/indexroo.htmlEarly Australian stamps - both the Roo's and KGV issues are popular and studied in depth. If you are looking for the most basic listing of "Roos," the Scott catalogs provides the most basic catalog using colors, values, and watermarks. Other catalogs go into more depth. I believe that are roughly 15 different color+denomination varieties if you exclude the watermarks. However, a change in the watermark can have a huge impact on the value of the stamp.
Paul