Can a Ritual Caster guide another person without ritual casting to make a ritual spell?

Question

Can any caster with ritual casting, or a character with the Ritual Caster feat guide another person to make a ritual?

For example, a Wizard guiding a Rogue to make the ritual spell of find familiar or so.

Answer 1

No.

Nothing in either Rituals section, Ritual Caster feat or in Ritual Casting from the classes says anything about being able to guide someone else. Also, note the emphasized part below - it states explictly that the spellcaster must have a feature that allows him to do it. Rogues don't.

Certain spells have a special tag: ritual. Such a spell can be cast following the normal rules for spellcasting, or the spell can be cast as a ritual. The ritual version of a spell takes 10 minutes longer to cast than normal. It also doesn’t expend a spell slot, which means the ritual version of a spell can’t be cast at a higher level.

To cast a spell as a ritual, a spellcaster must have a feature that grants the ability to do so. Classes that can cast rituals as a class feature include Barbarian, Bard, Cleric, Druid, and Wizard. The Ritual Caster feat also allows any class to cast ritual spells from one of the following classes: Bard, Cleric, Druid, Sorcerer, Warlock, or Wizard. The caster must also have the spell prepared or on his or her list of spells known, unless the character’s ritual feature specifies otherwise, as the Wizard’s does or while using the Ritual Caster feat. Pact of the Tome Warlocks with the Book of Ancient Secrets Eldritch Invocation may also cast any ritual spells they find and add to their book.

Note that, from emphasized part, you also can't just guide someone into casting a spell they don't have - if that's what you were thinking about.

Answer 2

No.

Here's the rule on casting spells as rituals:

To cast a spell as a ritual, a spellcaster must have a feature that grants the ability to do so.

That can be a class feature (like a cleric or a wizard has), or it can be a feat like Ritual Caster. But it must be the character casting the spell that has the feature that enables the ritual, not some other caster helping them.