How do I rotate without losing the ends of the image?

[HavingTooMuchFun]

I wanted to use this specific piece of an image:





I wanted that streak of light to be VERTICAL, though, so I rotated the image, and got:





As you can see, the uppermost and lowermost bits of the image are missing. How can I rotate an image and end up with the ENTIRE image after it’s done?