Hello, everyone. I'm new to the forum and to gardening. My husband got me a beautiful mini rose bush for Valentine's day, and, unbeknownst to me, this plant actually consisted of three small rose bushes. They got root-bound pretty quickly, so I replanted them in a miracle grow soil that they really like in a larger pot. The plant has been doing fantastic so far, growing like crazy. I'm afraid it's almost time to replant it again. I was thinking about planting it in a large pot for its permanent home. It got blackspot a few days ago (we live in Florida where the humidity is nearly impossible to beat)... but I caught it early and sprayed it down which seems to have, if not completely eliminated, definitely helped the blackspot.
My question is, should I replant these plants individually or keep them together? I am afraid that if I try to break them up I might damage the roots, but I am also afraid that if I keep them together they won't have enough room to "breathe" after rain and may be more prone to blackspot.
I need help!

Thanks in advance!
Also, I inherited several beautiful planted rose bushes with the house my husband and I just bought, but I can't seem to fight off the blackspot they keep getting. I spent hours picking off diseased leaves and throwing them away, and even sprayed with fungicide a couple times (not very organic of me, I know... typically I'm much more environmentally friendly than that), but the blackspot doesn't seem to want to go away. Any suggestions?
-Ashley