Look at the work between job titles
Take the next project. Alongside the main tasks, write down who clarifies the problem, proposes options, connects people across departments, checks the details, and follows decisions through. Ask who did that work on the last two comparable projects and who could pick it up if they were away.
Add a recent example to the map
Suppose three team members readily generate ideas. After the first demo, customer comments disappear because nobody pulls them together. For the next launch, name someone to collect the feedback and identify decisions for the second version by Friday. The role map can help you identify who might take it on, and the outcome will show how well the arrangement works.