After lots of painting for a number of years all I can recommend is tape and don't be cheap. Buy a good paper tape machine, especially one that will hold wide rolls of paper. To tape the roof use the blue tape which will hold in a hurricane. Tape just at the facing edge and wrap over the top of te tile. The overspray should not stick beyod 24 inches. Just spray up toward the roof and not down toward the house when working near the roof line.