I have a 5 yr old Rosa and have Nina in mind if I ever had another girl, so I would say definitely yes. A longer name would be less 'matchy'..but honestly, I don't think that's the first thing people will think of when they hear her name
I love Rosa. Elegant, and unusual without being weird. Beautiful. I know what you mean about matching with Nina, but I think they actually work quite well together. They do sound similar, but also individual.