Don't know for sure at all but I'll assume Brockington and Conditt move on, Gabe and Jaz, maybe Tristan are back. Tre and Jaden transfer somewhere they'll get a better chance at more playing time.
I think Rob has improved as the year has gone on, but his best role is going to continue to be a hustle player who isn't relied on as a starter. He can be a great enforcer off the bench type, 15ish minutes a game, come in, play hard defense, get some boards, etc. Bringing in a 5 with more ball skills would be a great fit for the offense ISU ran this year, and I think it's something we'll see TJ and his staff pursue. Obviously those guys are usually recruited by everyone, so it's no easy task, but I think it would work wonders for the offense.
Just as important, I think you need to find another guard/wing who is comfortable with the ball in their hands generating offense OR one that you can run more sets for, think coming off of screens for open threes, etc. Ideally, you can find someone who can do both, but easier said than done. IMO, a lot of problems on offense this season came from guys not being comfortable with the ball under defensive pressure. Lipsey will help as a backup to Hunter, but I think an experienced player who can create space through garnering defensive attention and being a secondary creator is another player type I expect to be pursued.
Obviously, I think Hunter takes a big jump as a player. He's shot from three much better as of late, and adding an 8-10ft floater would open a lot up for him.
Seeing that ISU is on the list of teams pursuing more than a couple guys already makes me feel like TJ knows there's work to do. I'm excited to see what the portal has in store.