Just re-read my post and realised it might sound like I was ignoring your roles workaround - sorry.
I was thinking that I might end up with a very granular application of roles where I had to apply a different role per component/per form. It’s ok if you just want to apply a border colour but adding other formatting quickly escalates the number or roles required.
I thought it might be easier to follow if basic formatting was kept within the form.
Another thought with regard to roles would be to allow multiple roles to be applied to a component. That might help the granularity aspect.
As you can probably see I’m using these posts to organise my disjointed thinking so appologies for that.
After a quick search it appears that multiple roles are allowed via code:
self.label_1.role = ['blue-text', 'bold-text', 'green-background']
I guess that is the Solution!!