Another thing that must be mentioned, or maybe more than one thing:
1 You must be able to play at (whatever speed you want to achieve)
mostly relaxed (you might not be completely relaxed playing very high speed runs but, all other speeds you should be,
if you are not, then you have not really conquered that speed and you might not be able to play it consistently all the time.
That, (playing consistently ALL THE TIME) is when you know you have conquered that speed.
2 Whatever speed you conquer be that for a drum roll or executing a paradiddle or double bass... they need to be usable in a musical situation otherwise they will not matter and will be just as useless and boring as a 16 min drum solo.
My example song would be Live Undead by Slayer because it has everything, a slow steady beat (you need to be able to play that first slow part cleanly as well then there is a double bass (slow as well) then it goes into this faster rolls and finally explodes into speed. If you can master playing that song correctly then faster songs will not feel as daunting and impossible to achieve. and just because you can't do it a present time doesn't mean you won't be able to do it with some practice.
First example is a cover but the original drummer is Dave Lombardo
The second example is a cover (of a couple of songs being Killing fields and Dittohead) and the drummer is Paul Bosthaph
The rolls at the end are killer.