It is my personal belief that I design a site FOR my client ON BEHALF of my client. My thinking is that once you have paid for the website, then that is yours to keep or change as you see fit. I think it is only fair to give credit to the design firm somewhere on the site, and the client is not authorized to re-use or re-sell the development code or website.
The same goes for clients hosting through Digital Rose ... the website is still yours, so if you decide you want to go to a new host or developer in the future, the site is yours to move to the new host/developer whenever you like.