I think there's a very good chance that this very thing occurs. We need Grant to get better for the long haul, but focusing on the here and now there is a tremendous opportunity ahead of Roberson. He's inexperienced but has fresh legs. He's supposed to be an above average rebounder. Both of those things could help reverse some recent trends.
Really excited to see what this kid can do, and curious to see if he somehow carves out a mini-niche that enables JB to "bolster" depth for the stretch run by one additional player. Maybe Roberson plays well enough to continue starting, enabling JB to bring Grant off of the bench once he returns, giving us a luxury scorer as a reserve.
The key will be for Roberson to focus on the things he can control, and not worry about scoring / shots. Rebound the ball. Play your area of the zone. Provide weak side shot blocking. Those things play to his strength. Then, get out on the break, run the floor, and look for transition scoring opportunities / putbacks. Don't try to do too much. Defer to the veterans on offense and let the shots just come in the natural flow. If he does those things, he'll be fine.
Will be interesting to see how it plays out.