Looks amazingly like your RockiMtn
name would suggest.
Forward seatclamp, Sloping Top Tube and long extended seat tube, wishbone stays, noodle style routing is something they played with, Ritchey dropout where used on their higher end bikes, hand stamped frame number is also something they did. (cannot see the left hand side numbers properly).
Not saying it is as so do a few others, but I woudl say the gear cables are running down the worng sides (j/k)
Though I forget to add what makes me think it is not an RM.
There would be a hole in the stays part, I do not remember seeing that style noodle routing on anything other than say a KONA, god forbid
Sod the edit on my way to the loo 1993 RM Blizzard was black/white, filled in dropout (as they did in '93), very sloping, short wichbone top...
Think that may be it, not sure on the rear noodle though.