Rose Cutting - Question?

Hi everyone, I'm still very much a beginner especially when it comes to cuttings (except for Dicentra/bleeding heart plants, they seem pretty fool proof) However, I took a cutting off a rose bush last summer and to my suprise it rooted, it has grown pretty well (it now has its own little thorns and everything ) My problem is recently a few of the leaves are starting to look a little unhealthy and are yellowing slightly. When should such a young plant be planted out where it is to grow permanently? How many years does it take for a rose plant to grow large enough to flower? And is there anything I can do to remedy the leaves if it's too early to put it outside? Thanks in advance :patpat: