Hi Greensail,
this is no answer to your question. Like you, I'm waiting for someone who has some explanation. Like you, I can play singles fast enough to compete with any doubles (except my own). Clearly, double stroke rolls have a different expressive quality, so there must be appropriate applications. To me, double stroke rolls sound more machine-like, almost merciless, and aggressive. Now, agressiveness doesn't have to be something negative, particularly as far as drumming is concerned.
What emotional quality do double stroke rolls incorporate for you?
We should consider that double stroke rolls are not traditionally part of the conga vocabularly. They come from the martial repertoire of the snare or side drum. In drum set playing, they may at times appear in solo passages like fill-ins. This is not exactly transferrable to the conga drum. Whenever a conga player chooses to play a fill-in, he/she should take care to not clash with the drum set or timbales player.
The best start might be to study the pioneers and practitioners like Giovanni. I think Angá used it, too; but with Angá, I also hear a lot of Changuito's left-hand "mano secreta", which was more or less the forerunner to this technique. Pedrito Matrínez uses doubles effectively and very musically at moments where they really make sense. More than any other feature, the use of double strokes are marking the so-called new school of conga playing. After all, you may ask yourself: Does that fit my own language? These are great players, but would adapting
their stuff make
me a better player? Or a worse musician, even?
I have answered this question for myself long ago. Anyway, I kept on practicing double stroke rolls, because it's good for my hands.
Thomas
P.S.: Patryk from Poland has posted a video of his solo on this forum, and he uses double stroke rolls occasionally:
http://www.mycongaplace.com/forum/eng/viewtopic.php?f=35&t=9934.