I have a light switched with a normal one way light switch and want to loop in an extra light from the same switch.
Do I just omit a switch wire on the extra lights rose after it's added to the circuit or must I loop it in slightly different?

All you need to do is run one pair of wires from the first light to the second light. If the first light has 4 wires to it, you have to determine the ones connected to the mains with the switch in the on position, and connect them to the second light.