Oracle Database Discussions

I'm trying to design access to database objects in oracle using a .NET app. I've set up a users who are assigned to a role - MyRole - which is given execute rights on pkgMyPackage, however when I try and access a procedure or function in the package as a user assigned MyRole I get the error detailed above - I saw one posting and it mentioned that if privilages are granted only via a role, then this is expected and documented behavior. How does one use roles to control access to data / objects or am I barking up the wrong tree?

Any help much appreciated by this newbie