Need Information on RBAC in context of application access

Hi Gurus,

We are evaluating implementation of 'Role based access control' functionality to move away from the conventional function based security...Need guidance with the following:

1. What are the pre-requisites for RBAC i.e. Application Version, major patches?

2. Can RBAC be implemented selectivley i.e. on an instance with 25 modules, can we choose to implement RBAC on only 5... or it gets implemented for all?

3. Is some 'RBAC compliance' needed from each application module to be able to rollout the feature for the module?

Any answers, reference to myOracle notes/ blogs/articles will be appreciated...

Thanks

Amit