I'm playing as a Wizard, currently level 5.
I'm developing only magic skills.
Questions:
-Where can I find a scroll/resurrection spell?:confused:
-How do I put troops into reserve? How many reserve slots can I have?:confused:

I completed the game twice as a Warrior, the first time on Medium difficulty, and the second time on the second-to-last difficulty (I don't remember what it's called).
On Medium difficulty, I found the resurrection scroll in the lands of the Dwarves (when I was looking for the Dwarf King); the scroll was in a chest.
On the second-to-last difficulty, I found this scroll when I was looking for the "Lucky One."

Regarding the reserve: this ability is in the Spirit skill tree, and it can be upgraded twice. The first upgrade unlocks 1 slot (an icon will appear next to the army indicating the reserve), and the second upgrade unlocks a second reserve slot.