Being back to the forum after some time and glad to see new riddles here.

So here's my guess: It might be Holy, or the white materia

I hold everything
Beauty, magic, power, blessings ----> The white materia looks beautiful, is a powerful magic materia, and holds the bessings of aeris within
I slip, I fall ----> refering to the scene where you see the materia falling down into the lake
All is released
Like rose petals scattered in the wind
At the end ----> May mean the end, when Holy/ the power of the white materia is released and the lifestream ist coming from all over the world to fight off meteor.