Rovers raced into a two-goal thanks to a brave diving header from Sophie Jones and a first of the afternoon for Sheen, only for Cardiff to peg the hosts back by the break.
But Rovers upped the ante after the interval, with Sheen completing her treble and Lynda Shepherd and Katie Anderton also getting on the scoresheet.
Manager Gemma Donnelly said: “Cardiff were a young and organised team, who never gave up. Until we rang the changes midway through the first half, we demonstrated sheer dominance and a 2-0 lead was the least we deserved.
“The purpose of pre-season friendlies is to ensure the team gel and to experiment to find an effective style of football. Ordinarily we wouldn’t change things if they were working well, but to give certain players, including trialists, a run-out, we sacrificed our three senior players and Cardiff responded well.
“When those players were reintroduced with about 25 minutes to go, from that point on, the football we played was attractive and attacking, and we posed Cardiff countless problems. In the final few weeks before the start of the season, we will concentrate on tightening up defensively and tweaking certain elements to the team.
“We have won all our pre-season fixtures so far, but we have set ourselves a tougher challenge in the second half of pre-season. All the teams are in different divisions to us, but everyone is aware of the requirements and demands to give 100% both individually and collectively.”
ROVERS: Hutcheson, Taylor, Middleton, Twohig, McLellan, Shepherd (Holbrook), Westerman, Fleming, Anderton (Shaw), Sheen, Jones (Hallows).