A roach is the unsmoked end of a joint, blunt or spliff that is too small to hold comfortably, usually less than 3⁄4 inch long. Roach size varies based on personal preference and technique. Some use crutches or roach clips to finish smoking roaches completely, getting the most out of leftover cannabis. Others discard roaches earlier to avoid resin accumulation that can make the last hits increasingly harsh and unpleasant. Saving roaches in an ashtray can provide leftover material to smoke later when fresh weed runs low.
Determining when to retire a nearly finished joint/blunt into the roach ashtray depends on personal taste. Some don't mind the buildup of tar and associated bitter taste, allowing roaches to dwindle down to a tiny nub to maximize usage. For others, resin starts negatively impacting flavor once roaches reach a half-inch or so. Knowing when the smoking experience deteriorates into pure harshness is learned over time.
The thickness and density of the original rolling paper or wrap also influences how long a roach can be comfortably smoked. Thin papers like Elements burn quicker than thicker wraps, producing smaller roaches faster. Slow-burning hemp wraps yield longer roaches with more usable material leftover if desired. Overall roach size varies, but the end of a roach signals the conclusion of a particular roll, ready to be discarded or saved based on preference.