Can I roll and then use fatigue for hero or allies if needed?

By Pyth, in Runebound

Hello a couple of questions:

1) Can I roll and then decide to spend fatigue to add to my roll with hero or ally abilities or do I have to spend the fatigue before rolling and take the chance?

2) If an event that is a lower level appears and I discard it, do I still refresh the "starred" adventure runes on the board?