STILLWATER, Okla. - The first two pieces of Oklahoma State wrestling's 2000-01 recruiting puzzle are now in place.    Jake Rosholt, a 184-pound prospect out of Sandpoint, Idaho, and Russ Blackmon have signed national letters-of-intent with Oklahoma State.    Rosholt, widely considered the nation's top recruit is expected to wrestle at184 pounds in a Cowboy singlet.    "This is a great start to our recruiting class," said head coach John Smith. "Jake and Russ are outstanding wrestlers, and we are very excited for them to become a part of our program.2    Rosholt was tabbed as the nation1s top prospect by Intermat and the top 171-pounder in the country by Wrestling USA Magazine. He won the 171-pound weight class at the Junior Nationals last spring, laying claim to the outstanding wrestler award.  Rosholt will go in search of his fourth state championship in the spring before joining the Cowboys.    Rosholt chose OSU over Iowa State, Iowa and Minnesota.    Blackmon, a 174-pound prospect out of Cleveland, Tenn., also inked with the Cowboys. He won his first Tennessee State Championship last season as a junior.