The issue won't be the size of the fee to release him, ffs, c'mon, we're not that skint, despite what the doom mongers on here say!
The reason will be (like I've been banging on about for ages) is that Sheff Wed owner is a nut case, and he won't be making his release easy.
If he feels, legally that Rohl will be in breach of their contract, if he walks away or even resigns, then he may stick by his guns and no one may be able to employ him! - Contracts can be a complicated thing.