I have started to notice on a couple of new roses that I have planted that  when  the roses get about 3 - 4 weeks old after they have leafed out nicely the leaves dry up turn black and the rose appears to have died.  They all have been warrantied by J and P but i'm not sure if i'm just getting a bad one every now and then or if i'm doing something wrong.

Has anyone else had this problem? 

The roses that have had this problem are Sisters at Heart, Solstace, Tuscan Sun Gemini.

Thanks