Mike,
My guess is that if they had a DR designed course, they would have touted it, no? While the plan is similar in style, I recall many searches of old courses up in Chicago where the drafting style was similar, but it turned out to be some local landscape architect. Then as now, I wonder if a park district course would always hire an architect, much less a signature one.
I played Rackham and Rouge a few years back. Rouge didn't strike me as having any architectural genius or similarity to Ross. If it did, I do think there are many cases where some of the big name guy shapers or crew managed to find their way to other projects as side jobs, or between Ross jobs, whatever.
I will point out I am merely speculating.