The RCA plug may be feeding video back to the television, and then you'd have to get sound from whichever set of speakers is in the bedroom. You would start a dvd, and tune the television to AUX 1, or 2, or wherever the RCA plug is connected. (may say video 1, or 2)
The coax will be connected to the roof top antenna, and/or cable input. The coax will have nothing to do with the dvd.
2012 Ford F250 ext. Cab 4x4
2002 Jeep Wrangler Sahara
2008 Yamaha V-Star 650 Classic
2008 Work and Play 18LT