Hampshire scored a try and seven goals from as many attempts before being replaced by youngster Declan Sheehan 12 minutes from time.
Tigers’ full-time conditioning showed in the opening period, when they were too big, fast and powerful on a heavy pitch.
But to their credit, Rovers showed impressive spirit and some fine finishing to win the second half 28-12 after trailing 36-0 soon after the interval,
Four of Tigers’ off-season recruits got on the scoresheet, with Ben Crooks, Joel Monaghan and Greg Minikin also crossing.
Cas scored five tries in the first half, Hampshire combining with Mike McMeeken to create the opener for Crooks before Monaghan swatted off Rovers full-back Louis Brown to cross on his first Tigers appearance.
Junior Moors sent Minikin over after Tigers created a four-on-on overlap and then Hampshire crossed from Will Maher’s offload after Rovers failed to find touch with a penalty.
On the final play of the half Hampshire’s outstanding pass was finished by McMeeken.
Both sides were reduced to 12 men early in the first half when McMeeken and Rovers prop Darrell Griffin were sin-binned following a brawl.
Griffin, signed from Salford Red Devils, was fortunate not to be red carded after throwing the first punch.
The Championship side did have a couple of chances in the opening period, Matty Wildie being kept out by Paul McShane, before the same player held him up over the line.
Full-back Ash Robson impressed for Tigers, scoring a classy try soon after the break when he gathered his own grubber kick between the posts, but the hosts lost their shape as coach Daryl Powell made a series of changes and gave a run to several youngsters.
Sam Day went over from acting-half to get Rovers off the mark, Anthony Thackeray converting, but McMeeken dragged several defenders over the line with him for his second try, which completed Cas’ scoring on 48 minutes.
Thackeray, a former Tigers player, displayed impressive pace to race 70 metres for Rovers’ second try, which he also converted, after intercepting Hampshire’s pass.
That was the first of four consecutive tries for the visitors. Colton Roche crossed from John Davies’ pass close to the line, Kyran Johnson, adding the extras and then Johnson touched down from a pass by Michael Channing, who pounced on Crooks’ error.
Johnson completed the scoring with a converted try after Channing pounced on another Cas error and supplied Bradley Tagg, who sent the winger racing away.