Normally, in a situation where the GM doesn't want to commit long term big $$ to a young player, a short term deal is worked out for a lesser amount, with the tacit understanding that at the end of said 2-3 year deal, the player will be in line for an even larger payday if he proves his worth. That's what they should be doing right now, IMO- something like a 2 x 4.5M deal.
The trouble is, here, that Rossi will feel that Hynes will marginalize his role, minimizing his future worth, because of what he did in the playoffs, playing a worse performing player above him in the lineup. Since Rossi has no arb rights, all he can do is either hold out(which would be cutting off his nose to spite his face), or sign an offer sheet.