It is rare these days to find televisions that have analog audio outputs on them. You will likely be very hard pressed to get audio from your TV into the receiver unless the owner's manual specifically states that it has analog audio output. It is more likely that the TV has a optical audio output. This is a common connection these days for sound bars and for connecting to surround sound systems.
While your Rotel is a solid piece of gear to listen to analog stereo audio, it is the wrong product to be using in a audiovisual setup.
Your easiest option would be to see if your TV does have analog audio output (unlikely), and then use that.
If it does not, and you aren't ready for a new A/V receiver, then use the optical audio output from the TV and run it into a digital to analog audio converter...
Use this cable from the TV to the converter:
Then a set of red/white RCA cables to take audio to one of the inputs on your Rotel.
If your cable box is the only thing you need to get audio from, then you could run analog audio (red/white RCA connection) from the back of your cable box into a set of inputs on the back of the Rotel. You will want to be sure volume is turned up on the cable box to properly feed quality audio into your Rotel if doing this.