O'Boyle previously was under contract in Australia.
Brown is the top ranked player in Pennsylvania, according to the 247Sports Composite rankings.
Rogers wasn't rated by any major recruiting sites at the time of his commitment.
The contract promises a 20% raise for employees over four years.
Retherford will compete in his first Olympics in the 65-kilogram freestyle category.
Off-court Oilers fan and on-court big man Ward has taken strides since arriving on Penn State's campus.