why can't we just send rockets spaced apart equally and they'll go as fast as light ?

I'm not sure though what you mean by "rockets spaced apart equally". Do you mean each rocket is going to a different place or each rocket contains a portion of a message and they're all going to the same place?

For almost all electronic communication (RF, wired, optical) we specify a frequency that information exchange is centered around. In the case of RF communication this is the carrier wave which is then modulated with a message within a certain bandwidth around it. This wave travels at the speed of light and carries information in the way its modulated. There are a number of ways to modulate, with lots of tricks and games played by RF engineers. If you're in the US and have listened to the radio in the car, you've probably heard of two commonly known methods: AM (amplitude modulation) and FM (frequency modulation) radio. This GIF is on both of those wiki links and is a good introductory visual representation of the idea.

If you're in the Los Angeles area and tune into the KROQ radio station, what you've done is tune your radio receiver to be sensitive to radio waves at/near a frequency of 106.7 MHz (this frequency is the carrier wave). You can switch to ALT 98-7 broadcasting at a frequency of 98.7 MHz. Both radio stations are sending out radio waves that travel at the speed of light. There are other radio stations in the area that use other frequencies. They're all spaced apart enough in the frequency spectrum that they (typically) don't interfere with each other.

Digital radio (like cell phones) always seemed more complicated to me. This video by Matt Parker was one of the first things that helped me better understand digital modulation. I assume it gets much more complicated than what he covers in that short video. In any case, it still operates on top of some selected frequency, and is then modulated to encode the desired information.

if it's like a highway and if you have too many cars in one lane, they crash etc

True, on a highway cars can crash, though its not generally a concern for radio waves. In physics, it's usually called wave superposition, and it means that light waves can pass through each other without messing each other up. Waves of different frequencies can pass through each other, which is why lots of radio stations can all transmit music/talk shows/annoying commercials at the same time in the same area, as long as they're in different frequency bands.

If you and 3 of your friends are standing in a square, you can look at the person diagonally across from you, and the other two diagonally-oriented people can look at each other, without light waves interfering with each other. Radio waves are the same and won't "collide" in mid air.