Can I not add VIEW SERVER STATE to a role?
Just because you create a role in the master database doesn't make it a server level role. It's still a database role - it just lives in a really important database.

SQL Server 2008R2 simply didn't have user defined server level roles. For that feature, you'll need to upgrade to SQL Server 2012.

You asked for something authoritative, and the best answer there is good ol' Books Online, where they list what's new in SQ Server 2012 security features:

https://technet.microsoft.com/en-us/library/42919d6c-1fd4-466e-ac75-d579248c07df(v=sql.110)