I think this is a wonderful name; really historic and lovely-sounding. Personally, I pronounce it roz-a-line, which is the British English pronunciation. I think this name is definitely worth using, and would suit any age. :)
This is my favourite rose name. Rosaline has a soft and romantic sound, and a kind of dramatic and artistic beauty, without sounding over-the-top. It reminds me of the beautiful track _Baragoku Otome_ by Ali Project. I think roses are beautiful and I love Rosaline's ties to them. Despite Rosalie seeming like a blonde name to me, Rosaline makes me picture a gorgeous, but slightly creepy, Victorian doll-like Lolita with dark ringlets, thick-lashed brown eyes and a clear, porcelain complexion.