If it is actually a screw that is part of the horizontal section of the roof a better sealant would have been Pro Flex or Dicor lap sealant. If a vertical area then I would have used Pro Flex. Silicone is one of the worst for exterior sealant used in our industry; too much flexing and guaranteed to leak in no time. Original screw was probably over torqued.
Mike, RVIA & RVSA Certified Master RV Technician
Amy, Dr. Assistant - Roxie & Mei Ling, four legs each
2000 Gulf Stream Scenic Cruiser 450 hp & 1330# torque
06 Saturn Vue, 06 Chevy Z71 4x4 & 2014 Corvette Z51 M7