Studies have shown that roof sheathing with black shingles is 10 to 15 degrees warmer than with white shingles. That heat will work itself into the attic. However, there are now available high reflective dark shingle colors which you should investigate. They are Energy Star rated. In addition, your attic should include a radiant barrier attached to the underside of the roof rafters. This will reflect at least 95% of the radiant heat that would otherwise enter the attic and your home. The reflected heat slightly increase the temperature of the roofing, but is then radiated away outside. After that, a high quality solar-powered attic fan can reduce attic space temperatures further. Take care in that any attic fan can have a tendency to pull interior conditioned air from the living space up into the attic through ceiling leaks, somewhat decreasing the efficiency of any air conditioning. Careful ceiling sealing (pipes, light fixtures, etc) is important to reduce that unwanted flow. If you have any gas appliances, a leaky ceiling can result in retrograde airflow back down through flues, causing CO buildup. You don't want that. Pressure testing of your home could identify any problems. But, if these are not issues, then an attic fan can be useful. Then, certainly, you will want sufficient insulation in the attic space. R38 or so is usually recommended. Hopefully, you don't have an air conditioning system installed in the attic. Condensation associated with these can lead to moisture problems which cannot be alleviated by more attic ventilation. Hope this helps.