The most important part would be finding an actor for Roland who is on board to play the part for such a long timeframe in both mediums.
Supporting cast can be handled a bit differently, since they can figure out which characters they want to appear regularly in both, do occasional cameos, only appear in the movies, or shoot material during the films for the TV show or vice versa.
There are a number of different ways to handle it based on how they write/film/ and cast
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