Spell descriptions and cards that have a "ritual casting option" does not exist. If a class had ritual casting for that school, please add a filter on the spell list so they may view the spells that may be cast as a ritual. 

I'm not sure what you are asking for. When a class can cast a spell as a ritual, the spell has an [R] next to it.

Can you use an example?

I think they're (badly) asking for an option to filter spells by the ritual tag in the manage spells pane of the character sheet

Quote from Davedamon >>

I think they're (badly) asking for an option to filter spells by the ritual tag in the manage spells pane of the character sheet

 That could be it since that is literally the only place on the site where you can't filter. I don't think it is really needed there though.