When the open-minded; optimistic bud-smoker decides to not throw away the roach and use what's left of it. Usually what's left is placed into a relatively small piece or pipe and for the really determined ones, sometimes even stashed away for later when enough roaches equal a gram.
Pot-Head A: Hey you can throw that out man, it's just the roach. Pot-Head B: I'm gunna make your hair static if you ever say something like that again. Dude, we're goin to turtle it.