This question was inspired by this question about dealing with a creature protected by the Invulnerability spell.
Empower spell reads:
When you roll damage for a spell, you can spend 1 sorcery point to reroll a number of the damage dice up to your Charisma modifier
Sleep says that...
This spell sends creatures into a magical slumber. Roll 5d8: the total is how many hit points of creatures this spell will effect.
In the case of a single creature, the sorcerer is rolling for the sleep effect against the creature's amount of hit points (if one can isolate the targeted creature).
Is the fact that the sleep spell is affecting that creature's hit points equivalent to rolling damage, or is that a stretch too far in finding a creative use for the empower metamagic feat?
Answers that address Rules as Written and/or Rules as Intended and/or Rules as Fun are within the scope of this question.