A lesson learned that will stay with you forever. So it was a good experience. Trial and error are how we learn best. The grocery minis are a good, inexpensive way to practice.
All of those small grocery potted roses are just several sticks stuck in a pot and rooted. They are forced to bloom so they will be attractive and sell. They are meant to be like florist roses and, once the blooms die, tossed out. But they are real roses and with time and patience to grow them out can be planted in the garden. I don't try and separate them any more. Their root systems are so small and fragile that I found I lost all the roots just trying to get them apart. I just transplant them as is into the ground now.