Magic items ritual spells

[Hilary]

If you use a magic item to cast a spell, can you cast that spell as a ritual spell?

If so, under what circumstances?

What effect does doing so have on the magic item's spell slot? Is it consumed anyway?

Specific items would be a scroll and a ring of spell storing.

I am concerned with casting the spell FROM the item, not INTO the item in the first place.

This forum made it impossible to adjust the tags. It kept poping up suggested words. Someone needs to fix that.

[Kuulvheysoon]

Off of the top of my head, there's 5 distinct ways to cast (non-specific) rituals spells: As a prepared caster, a spontaneous caster, a wizard, the Ritual Caster feat and the Book of Shadows warlock invocation. Here's the relevant lines from the rules:

You can cast any bard spell you know as a ritual if that spell has the ritual tag.
You can cast a cleric spell as a ritual if that spell has the ritual tag and you have the spell prepared.
You can cast a wizard spell as a ritual if that spell has the ritual tag and you have the spell in your spellbook. You don't need to have the spell prepared.
You have learned a number of spells that you can cast as rituals. These spells are written in a ritual book, which you must have in hand while casting one of them.
You can now inscribe magical rituals in your Book of Shadows. Choose two 1st-level spells that have the ritual tag from any class's spell list. The spells needn't be from the same spell list. The spells appear in the book and don't count against the number of spells you know. With your Book of Shadows in hand, you can cast the chosen spells as rituals. You can't cast the spells except as rituals, unless you've learned them by some other means. You can also cast a warlock spell you know as a ritual if it has the ritual tag.
As you can see, all of them require that you know the spell; either by having it written in a special book, you Know it, or you have it prepared. Merely having an item that lets you cast it is insufficient.

[Unoriginal]

If you use a magic item to cast a spell, can you cast that spell as a ritual spell?

Nope, not unless the item specifically says so.

[Segev]

That said, I believe the ritual book versions all let you use a scroll as a source to scribe a spell into you relevant book, thereafter being able to use the normal book access rules to cast it as a ritual.

So it works for a wizard, a Book of Secrets warlock, and a Ritual Caster.