The Birmingham Mail have published a fairly comprehensive article
about their experience in the Rollercoaster Restaurant today. It does offer some insight into the pricing, with main meals cost £10 upwards (highlights that a Fillet Steak & Chips costs £25), while the kids meals come in a bit cheaper. This pricing fits with the Resort's intention for this to be their most premium dining option.
It does seem like it's going to be a (perhaps surprisingly) popular addition to the Resort, and it's nice to see some of the more geeky touches such as the ride plans and concepts that line the walls.