I almost always go the no romance route for these games. I vaguely remember in ME1 I told Ashley something along the lines of "Not now, but maybe when the war is over". The same thing with Tali in ME2. I like when the refusal options are practical like that and the other character doesn't throw a tantrum when you turn them down, lol.
Anyway, regarding the "something extra" for no-romance characters, I don't really expect anything, but I think there are some possibilities to do something cool.
Maybe for Dragon Age, an example would be it's the night before a final battle. Your companions will spend it hanging out with each other in the tavern or whatever and if you are part of a romance, you can spend it with your love interest.
But let's say you refused every possible romance, perhaps you could get a special scene like this:
The game will show the tavern filled with soldiers and some of your companions hanging out, enjoying what could be there last night alive. Some nice tavern music could be playing in the background. But then the scene would cut to your character sitting in a room, no music, just the sound of him sharpening his sword as the camera slowly inches closer and closer to him.
The scene would cut back to the other soldiers having fun, companions making jokes, etc. The music still playing in the background. Then it cuts back again to you, still sharpening your sword, the room silent, no music. Maybe the game will flash glimpses of other characters' faces that have died during your quest, hinting at the anger that is brewing within your character. But still the camera gets closer to your character's face.
The scene can swap again, maybe showing a couple of your companions that have their own romance laughing as they enter one of the private rooms for themselves. Then it cuts back to you and the camera finally stops in front of your face as the sound of you sharpening your sword finally stops. You finally raise your face to the camera, a look of pure hate and determination in your eyes. And the scene ends.
Basically, the above scene would be something for a lone, brooding warrior...which is basically every character that I try to make, lol. So while other character's would get their love scene, drawing strength from their companions, my character would get a scene like the above...a singular, unhealthy obsession with finishing the mission.
So yeah...just an example, and probably a crappy one, lol.