Powell confirmed in the wake of Featherstone's win at Batley that he was leaving the club after a successful four-year stint in charge, and is expected to be unveiled by the Tigers on Tuesday morning.
The Tigers recovered from 18-12 down to see off Rovers - rapidly sliding themselves with three defeats in as many league games. Liam Salter's two tries were scant consolation for Craig Sandercock's inconsistent group.
Rovers were boosted before kick-off, though, by the return of Craig Hall, while forwards Keal Carlile and Jordon Cox were recalled. For Cas, winger Kirk Dixon made his 150th appearance for the club, but there was no debut for Tyrone McCarthy following his loan move from Warrington.
News of Powell's impending appointment had filtered around the ground before the game, but Rovers started as if to dampen the mood, with Hall gathering a Rangi Chase kick, bursting clear and putting in Rhys Lovegrove. Michael Dobson goaled. In response, Dixon was halted 10 yards short of the try line after a delightful move involving Chase, Daryl Clark and Nathan Massey as the Tigers rallied. And with England stand-off Chase pulling the strings, Castleford began to to make most of the running.
Consequently it was no surprise when they levelled in the 15th minute, Chase creating the opening for prop Ryan Boyle to score his first Tigers try since he returned to the club from Salford City Reds. Jamie Ellis's conversion made it 6-6. The visitors did well to survive further sustained Castleford pressure in which Massey and Dixon were halted just short and Jordan Tansey had an effort ruled out after chasing Chase's kick. But Rovers then broke upfield to regain the lead in the 27th minute.
Travis Burns and Lovegrove went close before Salter plunged over from close range and Dobson converted. The Tigers had a let off when Justin Carney failed to deal with Dobson's high kick and Rovers substitute George Griffin pounced for a touchdown which was disallowed for a knock on.
As the play switched ends, Tansey then did well to gather another Dobson kick near his own try line as Rovers pressed again. But the Tigers bounced back to square matters on the stroke of half-time when clever play by Chase and Tansey saw Aussie winger Carney show his finishing strength by charging over from 35 yards out for a try that Ellis converted.
Rovers made a dream start to the second-half when they score immediately from the kick-off. Mickey Paea punished Castleford's mistake in allowing the ball to bounce by scooping it up to put in Salter for his second touchdown that Dobson improved.
The Tigers then turned the game on its head by roaring back with four tries in a blistering 13-minute spell. Michael Shenton crossed near the corner for an unconverted try in the 57th minute, before prop Jonathan Walker forced his way over, while Chase's long pass sent in Carney near the corner before Tansey weaved his way through in great style and Ellis kicked his fourth goal to put Castleford 32-18 up. Omari Caro's 80-yard interception try seven minutes from time and Dobson's fourth goal came too late to rescue Rovers.