I think Roscoe should stay in his Post.
Chopping and changing Managers never does any good (look at some Football Clubs I could mention). If you want success you have to be patient, and remember that the Team Manager is only as good as the material (Riders) he has to work with.
Roscoe has won the League with Swindon, so he knows how to win. He must be given the chance to do it for England.