How does a plane with rudder only do rolls?
slowly!!!!
i doubt if a slow stick will fly inverted, it has a heavily undercambered wing section, dihedral, and not enough roll authority from the rudder to keep it there once you get it inverted and it tries to 'fall off' due to the dihedral.
learn to fly on the slowstick first and get a model with aerobatic capabilites second.
the slowsticak will loop following a slight dive to build up speed, whether those foam wings will snap or not is anyones guess!!!