Yo Zeke- You are way confused. Let's simplify it- Webster's dictionary says coaxial cable is:
"A cable consisting of a conducting outer metal tube enclosing and insulated from a central conducting core, used for high-frequency transmission of telephone, telegraph, and television signals. Also called coaxial line ."
It is called coaxial because the 2 conductors are around the same center point, or axis. It's just a way of making a 2 (or more, I suppose) conductor cable. The monitor outputs on a Roland VS studio put out a line level signal, whether they have RCA outs or 1/4", or XLR, or whatever.
S/PDIF (Sony-Phillips digital interface) Is a way of sending a digital signal, usually audio, through a cable, to another digital device. The 2 devices must be synched in bit rate and resolution, and one must provide the "master" clock. The other clock is "slaved", in synch with the master.
There is also *optical* S/PDIF, which transmits the same data via optical fiber cable, but only 2 channels, unlike ADAT or Firewire, which can transmit many more channels.
Moving along- "Line level" comes in 2 flavors- 1. -10dBV and 2. +4dBu.
-10 is consumer level, what you expect to come out of a home stereo or a walkman, MP3 player, most camcorders, etc. +4 is pro level, usually used on recording gear. Usually (but not always), RCA jacks are used for -10 and 1/4" or XLR connectors are used for +4. Exception-
My VS1824CD has RCA monitor outs, for instance, but they are +4 line outs, compatible with a studio power amp or active monitors. Your 2480 has +4 monitor outs, but I don't know if they are RCA, 1/4" (my guess), or XLR.
The S/PDIF outs are RCA jacks also, but only transmit a stereo digital signal, 2 channels from one jack. In a perfect world, your stereo amp would have a switch for -10 or +4, as many recorders and preamps have. Most likely, you will run the +4 monitor outs of the Roland to the -10 RCA inputs on your amp, and you will have to turn down the monitor out signal to avoid overloading and clipping the home stereo amp. If you've been using it so far, you probably already know this.
The difference between -10 and +4 isn't really 14db, because dBV and dBu are different reference systems. I'm told the difference is more like 11db, but I don't know the exact figure, I'm a songwriter, not an engineer.
Short answer. All you need is the right cable to get from whatever the monitor outs are on the Roland Studio to RCA jacks, and you'll be fine. You should learn more about digital transfer, though, because it's the key to getting good sound out of a Roland VS studio or similar standalone. It allows you to bypass the Rolnd's preamps, and its A-D conversion, and send a clean digital signal straight to the Roland's hard drive. Then you send it back out, in the digital domain, for processing in the PC. At least that's how I do it. Optical S/PDIF is particularly cool, because it is not subject to electromagnetic interference, doesn't care if it's running over power cables, and doesn't pick up the radio. Hope this helps.-Richie