No and Yes. Casting spells from scrolls doesn't use a slot, it just uses up the spell and there aren't any limits on how many scrolls you can use.

Do all spells use spell slots?

Every class uses Spell Slots to cast their Spells. ... Some classes don't need to prepare their spells, meaning they can cast any spell they know, whenever they want, as long as they have the Spell Slots for it. Warlocks are the oddball — they don't have Spell Slots of different levels.

Can you use a spell scroll that is not on your spell list?

The general rule is that anyone who can read a language can read the scroll and attempt to activate it. This makes it so anyone can use types of scrolls that aren't spell scrolls, such as scroll of protection.