If there is limited space in your bedroom and you have a roommate, the best option would be a bunk bed. You have a lot of options to choose from given the various styles and models available in market today.
The Standard Bunk Bed:
This is the standard basic model for house bunk bed. There are two beds stacked with one directly on top of the other. There are different varieties in this style, and some smaller models designed especially for kids.
Twin Over Full:
In this type of bunk bed, everything is similar to the standard model except that the bottom part has a full sized bed. Two people of different ages and sizes can be accommodated in the bed at the bottom. Also if someone on the upper bed falls off, they will land on the larger bed!
The Loft Bunk:
This is most used in hostels, colleges and dormitories. This has only one bed on the top and work area at the bottom where a work desk or dressing table may be set up. In college, space is always limited and you are to use the same space for study, sleep and work. A loft platform bed frame lets you have both a bed (on the top) and a computer desk underneath) in one small area.
The Futon Bunk:
This is like a multi-purpose piece of furniture. Unlike the above two models, you get a futon that can be used both a couch and a bed (twin over futon bunk bed). It makes any bedroom much more versatile. Kids can share the room as well as use the couch for watching TV or playing games.
L-Shaped Bunk Beds:
This is similar to the full over twin bunk bed except that the two beds are not on top of each other but are set up perpendicularly and this leaves a little less floor space, but creates an alcove that can be used for dressers or a desk.