Roman Clemence is okay, although I don't like the flow much;
Roman Clemency definitely veers into "historical period where the Romans quit killing people".
For me, it's pretty much a girls name. My favorite combos are
Clemency Blythe and
Clemence Leontine.
"The secret garden is always open now. Open, and awake, and alive. If you look the right way, you can see that the whole world is a garden."