Actually the baggage policy is the same for sleepers as it is for coach passengers. And if one is traveling in a roomette (formerly the Standard Bedroom), then space is very tight. The Bedroom (Deluxe Bedroom) does offer more storage space, but even then, more than the standard two bags per person is pushing it especially on a Superliner. The Viewliner Bedroom actually has more space, even though there is no downstairs luggage rack like there is on the Superliner.

I've also heard that Amtrak is enforcing this policy rather uniformly. In fact I just heard a story of one conductor actually leaving someone behind who refused to comply.