The only reason to ground your two meter antenna would be for lightning.
If it were mine, I would simply do as you suggest, A copper or metal strap from the antenna mast to the roof.
HOWEVER, The roof itself NEEDS to also be grounded! At least at two diagonal corners with nice heavy wire or strap to 8 foot ground rods.
IF you "disconnect" any coax lines, DO put that "disconnected" line TO GROUND somehow, NOT just laying about in some kind of "insulator"!!!!! Think it over. A lightning bolt that just traveled several MILES through the sky will have NO problem blowing up whatever it is you have for an insulator!
For some good info on lightning protection see:http://members.cox.net/pc-usa/station/ground0.htm