Roark, 32, first arrived in Washington in July 2010, as a piece in the trade that sent All-Star shortstop Cristian Guzman to the Rangers.
Roark progressed through the minors fairly quickly, making his Major League debut for the Nats in Aug. 2013, when he pitched two scoreless innings in relief.
Arriving as an unknown quantity to fans, Roark proved himself to be a stalwart out of the pen, allowing just four runs and a .182 batting average against in his first nine relief appearances, pitching his way into a starting role at the end of a lost Nationals 2013 season. Roark broke from camp the next spring as a starter.
Rainey made his Major League debut in April and would make eight relief appearances across four stints with the Reds in 2018, pitching to a 24.43 ERA.