Is it possible to learn a spell or copy it into your grimoire from a scroll?

 

Not sure if I should just be using these as one-shot spells or hoarding the unique ones until I can learn them.

Scrolls are consumable-only. You can write new spells in your grimoire if you find somebody else's grimoire for 100cp x spell level. You can although, if you find somebody's grimoire with a lot of spells you don't know, decide to keep that grimoire instead of copying spells in your own.

Thanks