I have a 95 S-10 Blazer 4.3. In park it has a rolling idle and there has not been a CEL. Any help would be great.

You might try checking for a vacuum leak first.
Also the idle air control valve(IAC) maybe trying to stick. It also allows crankcase ventilation gasses into the motor and those gasses can sludge the port and pintle (plug valve) of the IAC. Removing and wiping the pintle & seat with a rag wet with carburetor cleaner unsticks it but don't spray the pintle & seat.