As much as Roger loves Illinois, I can't imagine him going from Associate Head Coach at a Power 5 school to basically the third assistant.
I trust your opinion as much as anyone's on here, but I can see Roger moving back to the Illini. In the majority of cases an AHC would not move to a 3rd assistant position, but this is different because:
1. We don't know for sure yet that he'd be third
2. His pay will likely go up either way
3. AHC for a rising mid-major may not be as attractive as a 3rd position on a team that could reasonably be E8 or F4 in a few years
4. As Illwinsagain mentioned, he may be attracted to learning a system that he thinks will be more successful in the long run.
5. It's homecoming!