You can treat it, but you cannot rinse it. Really depends on what membrane is underneath. Typically ballasted or IRMA systems are don with EPDM single ply rubber as the membrane. If you try to rinse, you will be there all day rinsing the stones, and might shift some around. You do not want to shift them too much as they are distributed in a specific pounds per square foot, to meet the buildings wind uplift requirements.