Rose mosaic is spread through the propagation of infected plants and does not spread from plant to plant in the garden. If you buy a rose with these symptoms, return it to your garden center. The virus that causes rose rosette is spread by mites. The disease is fatal to the plant. Keep plants clean, and spray with insecticidal soap to prevent rosette.
Crown gall is actually a tumor, bacterial in nature.
Cure by pruning off the tumor, but remember to disinfect your pruning shears afterward with a weak solution of bleach. Canker is a fungus disease that causes cane dieback. Prune away the affected tissue.