I want to get from kowloon Hong Kong to the rosedale in Guangzhou?

May I know where you are exactly in Kowloon?
Anyway, here is my general suggestion:
At Prince Edward, Mongkok or Tsim Sha Tsui Harbor City, take direct cross-border coach to Guangzhou. The stops in Guangzhou are saveral hotels and Rosedale is one of them. Therefore, the bus can take you directly to your destination.

You can easily get the tickets at the boarding site or book that through Trans-Island Limousine Service Limited Co. Search that online!