These exercises will help to strengthen your double stroke rolls. The sticking on all of these are single strokes (R L R L) while playing each slashed note as a double (as two 32nd notes). Practice these with a metronome and only play as fast as you can execute these comfortably. I recommend practicing these starting with both the right and left hand.
These first 4 measures have the slashed doubles displaces by a 16th note. Repeat each measure until you feel comfortable before you move on to the next and then play them in order, one after the other. If you have trouble starting with the doubles, play a measure of straight 16th notes to orient yourself and then play the intended measures.
Practice these consistently and you will see an improvement in your double stroke rolls.