Here is a video all about improving your Double Stroke rolls. I have found that the best way to improve your doubles is by practicing short groups of double strokes. These exercises build strength in the wrists and fingers.
There is an explanation error in a few exercises. I am playing 16th notes with one hand while playing the 4 and 5 note double bursts, not 8th notes as I state in the video.

Other videos on this channel that deal with this topic are here:
Drum Set Doubles    • Developing Double Stroke Rolls on the...  
Double Stroke and Closed Rolls    • Double Stroke and Closed Rolls  
If you search the word "Double" on my channel you will find several more solos that feature open rolls.
The books featured in this video are available from me at [email protected]
The sticks are 66-gram Zebrawood concert sticks and Cocobolo 85 gram chop building sticks with a barrel tip which I make and sell.
If you are interested in a pair, contact me at [email protected]