Double-stroke Roll

RRLL is all there is to the double-stroke roll, but as you play this rudiment, your technique varies depending on your tempo. At slower speeds, you can make two deliberate strokes, but when you get to a certain point (this speed is different for everyone) you need to start bouncing the stick once to get the second stroke. In order to get the second bounced stroke to sound the same as the first stroke, boost the bounce with the tips of your fingers by bringing your fingers into the stick as it strikes the drum the second time. One good exercise to play the double-stroke roll at a tempo where the bounces just start and try accenting the second note.
At the fastest speed, the double stroke roll will change again and turn into the buzz roll or press roll. The technique for the buzz roll is to press the sticks into the head, creating a ibzzzi sound.
One thing to keep in mind is that as the roll gets faster, your sticks get closer to the drumhead.