So, I don't see much more you can do with that. Rollins needs to stay heel; WWE needs main-event heels badly. They can't even keep New Day as heels.
You can do all sorts when it's a proper feud as opposed to a 'brotherly' contest. Ambrose claims he sold out, Reigns says Ambrose will never be a champion, off they go. They've got the chemistry already so all they need is a believable motive.
Unless they pitch it absolutely perfectly, I can't see Rollins coming back as anything other than a face. With the amount of heat that Reigns is continuing to get, all of the fans will jump on Rollins when he returns.
They are struggling wiith heels though, mainly as whatever they do with some of them, people cheer them anyway. Owens is a fantastic bad guy, as is Bray, but those two have got almost a 'cult' following who will cheer them and blur that line. HHH could have continued as the main heel on the roster, but he put himself in a feud against Reigns and ended up as the good guy again. So, bad booking is to blame for most of it.