When going straight at a roundabout, you should generally not signal as you approach or enter the roundabout. Instead, you keep your indicators off while approaching and entering. You only signal left immediately before you reach the exit you intend to take when leaving the roundabout. This left signal before exiting informs other drivers of your intention to leave the roundabout at that exit. If the roundabout has lane markings, follow them for lane positioning, but the signaling rule remains the same: no signal on approach and early left signal on exit. Some guidance suggests that signaling left as you exit helps other drivers understand your intentions and improves safety. In summary:

• No signal going into the roundabout if going straight ahead.
• Signal left just before the exit you will take.
• Keep in the correct lane according to road markings or signs.

This is the typical rule in the UK, Australia, and other countries following similar driving regulations.