There are times in which you move staff. Tell them you are expanding their agenda, tell them whatever you want.
Unless there is some stellar employee over there, one whom everyone compliments, don’t let members of staff get too comfortable/complacent.
There are employees who were hired to do this task. Sometimes you can add or subtract duties without dislocation, sometimes you have to be a bit more artistic in your statements.
For example, here was a chap hired to pack bags, but he seemed to have more abilities than that, so was moved to another post, a bit more responsible, and he filled it brilliantly.
If you actually know and watch your employees, you can find those who are just holding the job because they are financing their education or waiting to be called for training elsewhere.
Others will be with you until retirement.
If you are alert and have picked up various factors or have hired a trouble shooter to learn this, you won’t make mistakes by putting someone in charge of something and then they resign to do something else, or ignore that person for whom your business is their life.