I want to keep my desklight on when my roommate is sleeping
Why do you want to keep the desk light on?
I need the light to sleep
People usually sleep with the lights off. Make sure your roommate is okay with this because they can find the light annoying them.
It's fine as long as I don't bother him/her.
That's what you have to find out. Most people can't sleep with bright lights on as it annoys them. You might need to compromise with a night light or something.