Scrolls would be single-use items that allow you to cast a particular spell.  A scroll would disappear after being used.  Using a scroll would not expend any of your mana.  Also, if a spell has effects that normally vary based on the caster's magic score, a scroll would use a fixed number instead (fixed for each particular scroll, not a single fixed number for all scrolls).  This would make scrolls useful to non-mage characters, since they generally have very low magic scores.

Wands would grant +1 to a single spell.  For characters who don't have a particular spell, a wand would allow them to cast that spell, while characters who do have that spell will get better at it.  When using a wand, you still expend your own mana and use your own magic score.