Reply to Drum Roll Effect

So I keep hearing DJs during their live sets use, what i am guessing is either a beatmasher effect, or a sudden 1/16th loop. But the catch is if its a loop, then how do they continue the song as if they hadnt thrown down the loop. Meaning they do a drum roll with a loop (if not with beatmasher or something else) and after they release the loop it continues from where the song would be if the loop had never been dropped. How is this possible? I am sure its a very basic dj tool, so it would be good for me to learn how to do this lol, thanks!

Nasty Nate