Only the RZ Pro II has a RBL setting on the shutter speed dial. On the regular RZ (non-Pro II), it doesn't matter what you have the shutter speed dial on the camera set to when you use RB lenses.
You don't need any kind of adapter for RB lenses, but with an RZ, the back of the lens is closer to the film plane, so you have to open the bellows a little bit to focus an RB lens, even at infinity.
If you have a metered finder for an RB, you can use it on a regular (non-Pro II) RZ body, but not on a Pro II.