Mike from autogeek or Chris from Optimum would be the best to chime in on this topic.
need some details about you car.
Is it parked outside regularly? at night? how many hours each day is it outdoors?
Have you polished the roof any since the over-spray problem?
Do you have a paint thickness gauge?
It's a crap shoot.
one last thing... since applying the opticoat, have you tried claying the roof of the car? Then testing to see if the water will bead?
*I only mention this due to a few people thinking their coating had disappeared, only to find debris had stuck to the opticoat and prevented water from beading.