The days of ASP reports built on an IIS server are over. An RSP is now the sole means of reporting in CM12. For most admins, installing this role directly on the single primary in their hierarchy will be rather common due to simplicity and financial constraints.
Larger companies that have a Central Administrative Site (CAS) are also likely to install the RSP on the CAS for the simple reason that buying more RAM to get by is cheaper than managing another server for reporting.
Should you wish to offload this role to another server, the major requirements are x64 OS and SQL (IIS not needed). Review the CM supported configurations document at http://technet.microsoft.com/en-us/library/gg682077.aspx for up-to-date information for required OS and SQL versions. Performance will be directly tied to the speed of disk and amount of memory. A simple VM with 2 GB RAM is not a good candidate.
Because Microsoft SQL Server 2008 R2 is the most common version...