Of course, the main thing when you want to be seen is not to get carried away with the high viz stuff. Fortunately, I know when to say when.
'When' being, when I run out of reflective tape.
I find a well placed helmet light works a treat for Roundabouts
+1 on this. A helmet-torch on 'strobe' means you can direct light towards the threat, be it a roundabout or side junction. Of course, never, ever assume you've been seen though. I've had quite a few drivers do a sudden stop because they've seen the light at the last second. Something that I'm sure would not have happened had I been without the helmet-torch.