Protestant religions and Catholicism have a lot in common, mostly differing in the way that services/masses are held and some differences in praying. I think that as long as you're still respectful to what the rosary stands for to Catholics, there shouldn't be a problem.
Thenagain, if you want the tattoo purely because of how it looks, you can't really hold it against anyone for being offended that an important part of their religion has just been degraded to being an accessory.
I was once in a cathedral in Italy and they were selling rosaries outside of it. It was a group trip and a Pagan friend of mine decided to buy some. Despite the fact that I knew her beliefs didn't coincide at all with the meaning of the rosary, I still let her be because she had every right to buy what she wanted. But then she proceeded to mention over and over again about how she wasn't Catholic, but she just thought it was pretty and would make a nice necklace, and that was when I got seriously offended. But if she hadn't drawn attention to how blasphemous it was, there wouldn't have been a problem.
Overall, I think it depends on the reasons why you want the tattoo and what the tattoo means to you. Also keep in mind that if you want the tattoo based on the look of it that those are the kind of tattoos that people are more likely to have second thoughts about later in life; whereas if you get a tattoo that means something to you personally, you'll be less likely to regret it.