Hi Alyssa,
Heres a couple of ideas (try with the resin cameo you like the least):
1. Soak in water
2. Soak in acetone
If either of these steps works, it should only take a couple of minutes for the cameo to loosen from the frame.
3. Apply gentle heat.
If you have a toaster oven, you could try warming the piece up so that it might soften the adhesive. Be careful of fumes and I would suggest not using that toaster oven for food anymore.
Good luck!