Which paraphernalia might indicate cannabis use?

Roach clips are specifically designed tools used to hold a marijuana joint as it burns down to the end, allowing the user to smoke it without burning their fingers. This unique purpose directly relates to cannabis consumption, making it a clear indicator of cannabis use or possession. The presence of roach clips in a situation could suggest that someone has been using cannabis or has engaged in activities associated with it.

Other paraphernalia, while potentially associated with various substances, do not have such a specific connection to cannabis as roach clips do. Gel capsules might be used for a variety of medicinal or recreational drugs that may not necessarily include cannabis. Cotton swabs are generally used for cleaning or hygiene purposes and do not indicate drug use. Syringes can be associated with intravenous drug use, but again, they do not indicate cannabis specifically. Thus, the definitive link of roach clips to cannabis use makes them the correct choice in this context.