Hi FeFeCruise, welcome to Cruise-Chat. Sorry to hear about your problems, but do hope the rest of the cruise was fantastic. It sounds like they did try to offer you another room, even if it wasn't to your liking, they did try. Some of the comments, however, were inappropriate to say the least.
Please do as Maruine suggests and write a letter to corporate. Keep is as succinct as possible, with a copy of your pictures. It was probably rust or minerals, but they should have acknowleged your complaint. If they fixed it once (a little anyway), they should have been able to have fixed it again.
I do hope other than this, the rest of the cruise was enjoyable. I also hope you give Royal another chance, they are generally one of the top rated cruise lines. The 3 cruises I have taken on them were fantastic, and thankfully, problem free.
Best wishes and we hope you will cruise again in the near future!