Stylistically, I think the "R.N., B.S.N." looks better. Also, it seems like degrees are usually listed in order of acquisition or importance (as in, So-and-So, M.D., M.P.H.--the M.P.H. was acquired to abet the M.D., so it comes afterwards). I can't find anything in the style manuals that refer to professional degrees specifically.
The only thing that I think looks really stupid is people--like a nursing advisor of mine who has a serious case of "M.D. envy" and shall remain nameless--who put every degree they've ever earned after their name...e.g., Jane So-and-So, A.A.S., B.A., B.S.N., R.N., M.P.H., M.S.N., C.M.H.C., Ph.D. ("call me DOCTOR So-and-So"; I really, really wish I was kidding on this one, but I'm not. This is the same woman who spent a half-hour telling our advising class why we shouldn't go into nursing).