When you make a custom tactics in pro clubs, it does not make a difference on what role you give your player!
When you go into lobby, then tactics tab, it shows your formation but when you do the 'off ball view' and 'with ball view' your custom roles dont make a difference, even if they show, in game they dont work
we played with an attacking wing back to test this on one side and a full back on the other, they both played exactly the same.
so the custom tactics page shows one thing, the in lobby tactic page shows another, then in game it doesnt matter at all.