When you say role, do you mean an activity group within that role? If that is the case there are two options that I know of. Firstly you can add a transaction via PFCG, assign it to the base activity group and do a mass generation ensuring all derived activity groups are updated.
You can also use SE93 to add a transaction – There is loads of info on the internet about this.
I would advise you to look on the internet for each of the above subjects so that you get a definiative guide/documentation that you can follow.
Hope this helps