Crossroads is a collection of short stories, mostly from the Prophet of Panamindorah trilogy, though the last story in the book is a Cowry Catchers short about Silveo.
Most of the stories focus on the past of various characters, although there is one story that explains what happened to Syrill after his "exile" to Filinia. You really don't need to have read any of the books to enjoy the short stories, although if you don't at least know the terminology of the world, you might be a bit confused. It's definitely a better idea to read these at least after you've read the Prophet series, to understand what a shelt or an iteration are.
I'm personally waiting for a collection of short stories from Cowry Catchers. I know there's Professionals from this book, as well as Sky Dance, and Chemistry so far.