If the roof has the standard flat composition shingles then I suggest two 5 foot tripod antenna mounts . .
http://www.solidsignal.com . . PTV P5 tripod mount , and don't forget the pitch pads , . P10 Pitch pads. . Might use a chimney mount with one of the antennas. Find all manner of mounts and ect. at solidsignal. Also at
http://www.starkelectronic.com . . So as to stop the RG-6 coax from swinging in the wind , feed the coax up through the bottom of the antenna mounting pipe , out the top and connect to antenna , leave slack , no need to put sharp bends in the coax. Remember to use equal length coax between the antenna combiner and antennas. Mount the antenna while standing on the roof. Do not climb on the tripod to get antenna higher and higher and then you fall off. . Use a stud finder to find the roof supports , this way the tripod mount is very secure. . Many times I have used 'top rail' fence pipe as antenna mounting pipe , I get it at homedepot.