If people are doing the same activity, and so it is the same role, they can be affect in the same role. But there is the need to add focus to people, a different space time or physic zone, in order to put clarity. For example, a role, Account Manager, there is 3 people in it, they are doing the same role, but on different customers, so one would be with the focus of “Starwood”, another one for “Apple”, and another one for “Google and Amazon”. They are doing the same things, but in different space time, and so who have the authority is perfectly clear.
So in your case, the focus might be, Paul is affected in this role, but with the focus of this development project, and Pierre is affected in the same role, but with the focus of another development project.
There is also other possibilities, you can make a planning, with all the development project to do, and set a policy stating that anyone can, when finishing a development project, go to the planning, and take a new one, and so got the authority on that development project he/she choose. Giving you an example, in iGi Partners, we have a Video Editing role, we have many videos that need editing and we are two in the role. What we set, is a bunch of videos list that need to be edit, I personally select one, which make a project for me, and when I finish it, go back to the list of all the videos that needs to be edit, and pick another one. But it is clear who have the authority, what is my “territory”.
Have a nice day,