That is a good question. While Theo is worlds better, I
suspect it will be Nate... but that is speculation.
It makes sense for season continuity.
Assuming Berry/Paige was to be our backcourt, Theo was primarily gonna rotate in behind Jackson, and was likely to have gotten a few minutes at the 2 anyway. He would still do that in this scenario. Thus when Marcus steps back in at the 2 the rotation is essentially the same with Nate's minutes reduced back to what they would have been pre-injury.
Again that is speculation... still thinking like a coach .
On the other hand Roy could decide that if healthy, Theo's talent might prevail, plus it would be a chance for him to refine his perimeter game (which is his biggest deficit right now). I couldn't fault Roy on either course of action.
Now, this may surprise some on here, but I would personally lean to the first scenario... again for
continuity sake.
Either way, as you said correctly, the one constant HAS to be turning the keys over to JB and keeping this machine running as planned.