Help with Projector display

Sorry you are not describing it very well. Are you saying the image won't zoom big enough to fill your screen? In that case the projector is too close and will have to be moved back. Otherwise you would search menu options for screen and aspect ratio until you find the right match. 

Be aware that not all movies are in the same aspect ratio. Whatever aspect ratio your screen is, only movies that match that aspect ratio will fill the screen. But usually the part outside the image is black not white. So again not real sure exactly what you are talking about.

I use a 4:3 projector screen and roll down to the height that match other aspect ratio.

So when I project the screen is say 5 feet in height. Then I project a movie or tv shows from the roku or computer, the screen is filled 3 feet with the movie or tv, and 1 feet of screen space on top and bottom is still there which is just a plain projection or light. I have a picture but don't know how to upload here. Thanks.

What is the exact height and width of the screen?   What is the make / model of the projector. 

It sounds like an aspect ratio mismatch between the projector and screen.