Since the Lead Link has a domain on role assignments (unless you've changed this via policy), I would say that if Lead Link isn't in a tactical meeting, then you would create an action for them to do the role assignment. If you're in a governance meeting, then you won't be doing role assignments. Secretary only has permissions to assign roles in GlassFrog to assist the Lead Link (or other role if authorized by policy). Admins can also do role assignments, but again as an assist, at the request of Lead Link.
Assigning roles isn't a typical activity in a meeting. I'm not a coach, but if you are doing role assignments in Holacracy meetings as a typical activity, you may be misunderstanding what should be happening in the meetings.