How to flip the camera, but have it behave normally?

Edit :

I should probably explain a little better, since it doesn't make sense to allow a player to move the camera while also using :SetRoll.

I made a script that flips your gravity, so you're standing on the ceiling. I used :SetRoll to also flip your camera upside down.

I'd like to be able to move the camera around normally (hold down right mousebutton and drag it around), but have your camera be upside down at the same time.

What's the best way to do this?

I do not know if this can be done at all. When you hold down right mouse and drag it, I think that is built in to the game and unable to be changed. However, you could force first person to avoid the problem entirely, but that might not be what you want.