Traditionally in 5e, you can only cast a spell if that spell is on your class spell list.
That system isn't fun because it severely limits the options for non-spellcasters.

So here are the revised rules for Spell Scrolls:

A spell scroll bears the words of a single spell, written in a mystical cipher. a creature can read the scroll and cast its spell without providing any material components.
Casting the spell by reading the scroll requires the spell’s normal casting time. Once the spell is cast, the words on the scroll fade, and it crumbles to dust. If the casting is interrupted (such as Counterspell) the scroll is not lost.

If the spell is of a higher level than you can normally cast, you must make an ability check using your spellcasting ability to determine whether you cast it successfully. The DC equals 10 + the spell’s level. On a failed check, the spell disappears from the scroll with no other effect.