Roach

From MarijuanaWiki

A strip of cardboard that is rolled into a cylindrical shape and inserted into the end of a joint.

The roach has two main functions: to enable the joint to be smoked close to the end of the contents and, to prevent the rolling papers from getting squashed and impeding the flow of smoke.

Also, a roach can be the end of a joint that hasn't been made with a cardboard filter. The roach usually has the best weed due to the smoke making it full of oil and rez.