The ceiling rose (presumably you're doing away with it) acted as a junction box for the three cables. The cables would likely have been (are) - Power in to the Ceiling Rose - Power off to the light switch - Power off to the next ceiling rose.
Normally all the three reds connect together and to nothing else.
The red that goes off to the switch has a black wire coming back to the ceiling rose that's live when the switch is on.
This balck wire is NOT a neutral it's switched live and should be identified with a red or brown sleeve. It is this wire that delivers power to the light.
This switched live connects to one side of the light and to nothing else. The other side of the light connects to the other two black wires - the Neutrals - to complete the circuit.
If you can identify which of the black wires is switched live you're in luck - otherwise call an electrician.
You need a 4 way terminal block to replace the old ceiling rose. One "way" for the three red wires. One for the earth wires. One for the switched live. And one for the neutrals.
It is best and safter if the treminal block is in a plastic box of some sort but many people use electrical tape around the terminal block instead.
This picture may help you to see how it should be wired up...
http://www.diydoctor.org.uk/project_images/electrical_safety/ceiling_rose.jpg
They do not show the red sleeve on the switched live in the drawing but you can spot the four different connections (ways).
Good luck...
Peccavi, January 2009
