So there are no separate RDS CALs for R2, the normal Server 2012 RDS CALs are the correct ones to buy right?
No, you have RDS CAL for 2012 R2 which can deliver token to any RDS server (2012 R2, 2012, 2008 R2, 2008) RDS CAL for 2012 can only deliver token to RDS server (2012, 2008 R2, 2008)