Agree that Carberry is set to open. Root just looks more comfortable at 6, though in time, I'm sure he will move back up the order.
Root as a keeper is an absolute non starter, sorry. I would assume he was given the gloves based on either volunteering or as the most expendable of the top 6 batsmen if he got injured keeping. If Prior is out, Bairstow will keep, that's what he's there for. I agree that Prior will play and, to be frank, I'd rather have Prior on one leg with one arm than Root keeping in an Ashes Test match. I took up keeping for the first time this past season and I found the toughest part to be constantly focussing for every ball - for Root to do that in 25-30 degree heat over five days, not too mention the many technical shortfalls he will have (after all, if he was quality, he'd be keeping much more frequently) would be a monumental ask...
KP's injury is a concern long term, though I'm sure he'll play the entire series and they will manage his knee daily. IF he isn't fit, I see Bell moving up to 4, Root at 5 and most likely Ballance at 6.
I think the top 7 will be; Cook, Carberry, Trott, KP, Bell, Root, Prior. Worst case; Cook, Carberry, Trott, Bell, Root, Ballance, Bairstow. If the Aussies see the latter, they'll be smelling blood - lot of inexperience and low scores in there, though I don't doubt that Root, Ballance and Bairstow will be quality test players with long careers...