Most antennas can be mounted on a roof or inside an attic.
A medium directional antenna, for ease of mounting in any situation could be either a Clearstream 2 or 4 (see two other recent threads regarding the Clearstream line of antennas). At 14 miles the C2 would be fine.
To get stations in opposite directions, if using directional antennas, usually means two separate antennas. However some people will buy a directional antenna such as a bowtie and remove the back reflector to get signals from opposite directions. That however lessens the signal strength for all stations.
Your RCA multi-directional doesn’t pick up channels in opposite directions? What is the name of that antenna? Perhaps it needs a preamp. It should pick up Univision and Telemundo. An alternative would be an omni-directional antenna such as the Channel Master SMARTenna. That would pick up all the stations from all directions. Several Tablo users here use it effectively.
Two directional antennas would mean combining them with a splitter ($2) inverted to become a combiner. Since the desired stations are diametrically opposite each other, there should be no signal conflict combining the two antennas via a splitter\combiner.
Are all the channels (north and south) within a radius of 20 miles or so? If so, a good multi-directional such as the CM should do the job (with possibly an inexpensive preamp).