How to make a scene that fills the screen?

Other than following one or two 2D platformer tutorials, I'm completely new to Unity. Most examples I've seen typically involve scrolling, but I'm looking to create a level (room) that fills the screen, with no scrolling involved. When the player walks through (say) a door they are taken to the next room. Something like http://screenshots.en.sftcdn.net/en/scrn/45000/45360/bubble-bobble-nostalgie-21.jpg. (Bizarrely, Bubble Bobble was the first thing that came to mind!).

I'm looking for some tips to get me going on the scene design/layout. Is the "room" size important when designing the scene? Or can it be any arbitrary size (up to a point), with the camera being used to make the room fill the screen? How do you get this kind of positioning pixel perfect (i.e. up to the screen edges)?

 

You could try adjusting the size of the camera bounds to match the scene, but that would adjust the zoom as well, so it could get kind of confusing for a player to have the zoom change each time they enter a new room. There's probably a better technique, but adjusting camera bounds is the only technique I've practiced.