Specialized Rockhopper derailleur hanger needed.....which one?
I googled "specialized rockhopper derailleur hanger" and one of the links was

https://media.specialized.com/support/0000004464/0000004464_CG0421_hanger_fit_chart_rev2013.pdf

The Rockhopper table is on page 4 of 9 and looks like this

ROCKHOPPER
2011 2011 Rockhopper M4SL 26"/29er 9895-4021
2010 2010 Rockhopper SL            9895-4021
2011 2013 Rockhopper M4 26"        9895-4021
2006 2010 Rockhopper HT            9895-4021
2011 2011 Rockhopper Comp 29” HT LEFT  9898-4240    RIGHT 9898-4245
2010 2010 Rockhopper SL 29”        9895-4021
2008 2010 Rockhopper 29” HT LEFT   9898-4240
2008 2010 Rockhopper 29” HT RIGHT  9898-4245
2011 2013 Myka HT 29”              9895-4021
2008 2013 Myka HT 26"              9895-4021
2005 (Late) Rockhopper HT          9895-4021
2004 2005 Rockhopper HT            9894-4206
2003 2003 Rockhopper HT            989-4271
1996 2002 Rockhopper HT            989-4261
2003 2003 Rockhopper FSRxc         989-4271


So, with some exceptions, half of them use 9895-4021 which looks like this:



And is mostly in black with the odd silver one around.  

The earlier models all use different hangers, so you'll need to remember when you got it, and work out its age from there.  

Interestingly, wheel size seems to be unrelated.



EDIT OP says its a "specialized hanger 12" which seems to look like this: