The Office Communications Server 2007 R2 documentation has been online for a while although really only the client content. The server content has been loaded this week. I will share that due to logistics around the site the R2 content exists in the Server Products and Technologies hierarchy for the current time and we expect it to be under Office System again soon. I also noticed today that I was not able to successfully navigate using the left hand menu navigation so please be patient as that is also worked out.
While there are those of us who have been working with the product for a some time due to beta use, most people will be seeing the product for the first time and that is why I have highlighted the migration content explicitly. In case the navigation is still a problem this is the link for the top of the R2 server content hierarchy allowing you to select content in the main (content) pane. http://technet.microsoft.com/en-us/library/dd250572(office.13).aspx
Any guidance for those of us who don't have the hardware or budget for new certificates, to perform a "rolling in place upgrade", where each role is backed up, OCS R2 installed, and then the role restored?
TC, I don't see this as documented but I am not sure that this is as bad as it seems on the surface. OCS 2007 was a 32 bit solution and R2 is a 64 bit solution so even if you have 64 bit hardware, you would be running with a 32 bit OS which would require you rebuild that. Granted your question is still valid if you chose to rebuild that way, but I think it is that reason we didn't document it.
Is this information available as a .DOC download anywhere?
The docs have not been released to the web yet but they are planned, I do not have an ETA.