Hi all!a very interesting bit of to+fro there,my small contribution concerns a part of the name which might help a bit.
Pre 1100,s is going to be difficult ,but 'Ros',Rhus',Rhos',Rhoss',Rose',as you know all indicate Red,'as it is used for Russia.
Also ,(and I honestly hope I'm not teaching anyone to suck eggs here!)there is Roseland in Cornwall,Rhos in Wales,and almost directly opposite a Rhos in Ireland.
All well and good ?Maybe a look at Scotland,+east coast names may turn up a connection?
Even a plain Redman?
Twisted logic!Goggy