A little gas smell is semi normal on a carb engine in a garage. Liquid gas coming out is not. That would be a vented system problem. Wrong/bad gas cap or plugged vent. A roll over valve will probably not change anything. (I believe they operate by gravity not pressure) After you eliminate the pressure in tank, it will not leak liquid and the smell will be almost gone. Some systems need relief from pressure and vacuum, some just vacuum relief. Some caps allow suction when gas level goes down and pressure relief for filling tank and expansion. You may have mixed up system types with whatever you have as a tank/fuel delivery/carb or injection, in-tank pump or engine mounted pump, etc. As said, no coiling of hose/kinking/mounted too low/ID too small. Try leaving gas cap loose to see if it fixes problem.
