I really don't see it for Roy, even 4 seems too high for me.
The simple fact is that your 4 (especially in this England side) is going to be facing the new ball quite a lot of the time. There's nothing to suggest he's got the game to cope with it, and if you drop him down to 6 then you already have Stokes, Buttler, Bairstow, and even probably Pope who should be ahead of him.
Admit it was a mistake, chalk it up to experience and be thankful that it hasn't cost us the Ashes.
I'd keep Denly at 4 for now for the simple reason that he scored runs, but even in doing so I thought it was the nail in the coffin for him as a test player. He's got a tremendous heart, and stuck with it grimly, but his technique against the short ball is so woeful it's bordering on dangerous. Long term, Pope needs to get up the order and make that number 4 slot his.