I just did a search and was unable to find something about this. If I missed something, I apologize!

I've noticed on a number of my scores now that the balance of playback between the different hands and different drums is inconsistent. For instance, I currently have a triplet roll that currently runs: 2 2 1 4 2 2 with a right hand lead. Those two beats I can very clearly the RH, but the LH sounds (especially on drum 2) sound significantly weaker. Has anyone else noticed this, and does anyone have any recommendations for how I may be able to solve this issue? My specs are listed in the signature.

I haven't experienced that issue, but one safe bet would be to actually assign Live Velocities to all of the notes, then adjust accordingly. In this case, you might need to bump the left hand sample that you mentioned up a few. If you're not familiar with Live Playback and Live Velocities, the Sibelius documentation has plenty of info about it.

I have dealt with the exact same issue.  It's only with tenors though.  The rolls always sound uneven and terrible.  I never have a problem with the snareline rolls, just the tenors.

I'll poke around with Bryan's advice though.