Reporting on Project/Activity Rates is a separate ability from being a 'Reporter'. You will first need to create a custom Reporter role by copying the existing Reporter role. Default roles cannot be modified.
To copy the role head under Configuration to Roles. Click the "Create" button in the bottom right
In the top right select the role you want to copy, in this case Reporter, and click Load.
Change the name to something more descriptive, like Activity Rate Reporter. The name isn't important, but it's good to be descriptive.
You can modify the Groups it's in if you wish.
In Abilities find the Project-Activity abilities and select the ones you want this role to have. Rate Management means the user will be able to change or create Rates. Reporter - Bill Rate means they can report on the Bill Rate, and Reporter - Pay Rate is the same but with Pay Rates.
On the right select the user you want to have this ability and click Save.