A thickness of 0.1 mm sounds awfully thin -- like a flimsy foil -- but I don't know exactly how you intend to make the rose. How will the petals be formed? Are you going to bend individual pieces and expect them to hold their shape? How are you going to hold them together? Rivets? Solder? Some type of glue or epoxy? A variety of thicknesses would work, but narrowing it down to the right one(s) depends on getting a bit more info from you. Here is a guide that will give you an idea of how copper in different thicknesses performs:

Copper thickness guide

P.S.: There is no protocol on GardenWeb: you just register and ask your questions. The Metalworking forum is not very active, so this is why you may not have gotten a quicker answer.

Thanks for your response, and the link. Simply folding each layer of petals is my intended approach, with either solder or epoxy to stop them shifting on the stem. Yes, it does sound very thin, but someone at work told me that it should be fine to hold its shape, even at that thickness (thinness).

I'm going to try and scout out some copper I can touch, if possible. I just don't want to leave ordering online too late, if it turns out to be my only means of getting the copper.

Good idea if you can get your hands on some samples. A thickness of 0.1 mm is about 4 mil. The link I gave you shows visually what 3 and 5 mils looks like, and you can see that it is somewhat fragile, but it might work for the purpose you describe depending on how you intend to construct the rose. Good luck. I'll be interested to hear how this turns out.

That link was invaluable. For what I want, I truly don't want anything thinner than 24 gauge, which is about 0.5mm. There is a scrap metal place I've been told about; it's just a matter of being able to get there without having to tell my wife what I'm doing!

Glad it was useful. Good luck. I'd love to hear how this turns out.