Above the roof install a ANT751 antenna aimed at about 155 degree magnetic compass.
Here is how to aim antennas ,
http://www.kyes.com/antenna/pointing/pointing.html.
Discard the 2 antennas that are up there now.
For 1 or 2 Tv's a amplifier is not required.
For 1 Tv use no splitter.
For 2 Tv's use a 2 way splitter.
For 3 or 4 Tv,s use a
http://www.channelmasterstore.com CM3414 distribution amplifier.