Indeed--a sleeper redemption covers up to as many passengers as the maximum capacity of the room, and I find that this is what makes the sleeper redemptions so valuable!

For a roomette the normal maximum capacity is two adults, or one adult and two kids (or even four kids with no adults; presumably the adults are in an adjacent roomette)--although any of these combinations other than the first would be a tight fit. Similarly, a bedroom can officially fit three adults, although this would be an incredibly tight fit and you would be advised against it, even by Amtrak (I did a Viewliner bedroom with myself and my two small kids a few months ago, and while we were fine during the day it definitely got tight once the berths were made up).