This article on Amtrak Sleeper Cars is an excellent place for you to start your research on Amtrak long-distance trains' accommodations.
You can find a Viewliner roomette on Amtrak's eastern route trains. Although similar to Superliners, these roomettes are slightly different.
This page discusses 21 top questions I receive about rooms on Amtrak trains. The article covers various topics, including who shares your accommodation with, meals, and a suggested packing list.
Are you thinking of an Amtrak adventure? This article will help answer your questions on the Amtrak coach class on both regional and long-distance trains.