A ritual scroll is a single page of parchment, vellum, or paper.
Buying a Ritual Scroll: Like a ritual book, a ritual scroll can be purchased for the given market price.
Finding a Ritual Scroll: Ritual scrolls can also be found as treasure.
Creating a Ritual Scroll: You can create a ritual scroll by transcribing a ritual you have mastered. Creating a ritual scroll takes twice the amount of time as creating a ritual book but costs the same price.
Limitation: Even though a ritual scroll lets you perform a ritual, you can neither master a ritual from a scroll nor copy a scroll into a ritual book. A scroll is a condensed version of a ritual, partially cast and primed so that it only takes up a single page.
Using a Ritual Scroll: A ritual scroll holds one use of a particular ritual. You can perform a scroll’s ritual even if you don’t have the Ritual Caster feat, regardless of the level of the ritual. You still have to expend the components and supply any focus required by the ritual, and you can enlist your allies’ assistance. Once you have finished performing the ritual on a scroll, the scroll turns to dust. If the ritual is interrupted, the scroll remains intact.
Time: Casting a ritual from a scroll takes half the time indicated in a ritual’s description, since the creation of the scroll has primed the magic.
Published in Player's Handbook, page(s) 298.