You do not get -1g simply by rolling inverted. You have to remain in level flight to achieve that
You don't have to remain in level flight. Rolling inverted and maintaining the pre roll power setting and airspeed will see the aircraft accelerate into and establish a fixed rate of descent due to increased drag (symmetrical airfoils aside). Once the steady state inverted descent is established -1 "g" will be experienced. Accelerating to the steady state descent will see >-1 "g", -.8 as an arbitrary example.