No, good cases are NOT interchangeable between RT/SP; make sure the online listing you are viewing details that the case is for the Surface Pro, not the RT. The button layout is 95% similar, but there are a few differences - not to mention dimensional differences.
I use the Manvex Folio Case on my RT, love it so far. Manvex also makes this case for the Pro as well. Ebay and Amazon are your friend!