If I understand your question correctly, I think all you need to do is to shift right (not rotate right) the intial temperature result.

On the DS18S20, each count of the 9-bit result is one-half degree Celsius. In other words the least significant bit is the half-degree "count". After shifting right once, this bit is "tossed" and the least significant bit will hold the whole-degree "count".

Thereafter, you can process the result as an 8-bit whole number.