I don't think it's the brakes. the noise is higher on the car., if that makes sense. It really sounds like something is rolling but it doesn't roll back when i start back moving. I will check the spareIs the noise coming from the brakes? Does it only happen if the brakes are applied? In an isolated area where it is safe try applying just the hand brake and see if you get the noise.
Also, have you removed the spare tire and looked around in the well?