Fred Onyedinma's powerful header was the difference as Rovers suffered a narrow defeat in a first ever visit to Adams Park against Wycombe Wanderers.
The forward powered home a header just a couple of minutes into the second half from Joe Jacobson's dangerous corner kick.
The closest Rovers came was from Joe Rothwell, who saw David Stockdale in his way late on in one of the few chances the visitors had on target.
The boss made three changes to the team that started at Norwich City almost two weeks ago with Tom Trybull, Sam Gallagher and Harvey Elliott all coming in.
Those dropping out were John Buckley, Tyrhys Dolan and Corry Evans, who were all available as substitutes if required.
It was a lively start from both sides, with Rovers having to block bravely to ensure Thomas Kaminski wasn't tested as Wycombe threw everything at Mowbray's men in the early stages.
The first opportunity did go to the hosts 19 minutes in, but Admiral Muskwe somehow headed over the upright from a yard after Joe Jacobson's inviting corner picked the Leicester City loanee out at the near post.
It took a while for Rovers to test Stockdale, and the experienced former Birmingham City and Brighton & Hove Albion custodian was equal to Joe Rankin-Costello's strike that would have flown into the bottom right-hand corner.
The next opportunity came soon after, but Trybull nodded Elliott's corner over the bar when the German really should have tested Stockdale.
Rankin-Costello's afternoon was over with a couple of minutes to go until the half-time break, with an ankle injury forcing Mowbray to swap right backs with Ryan Nyambe coming on in his place.
With neither goalkeeper tested anywhere near enough, it was no surprise that the teams went into the interval scoreless.
However, it took just two minutes of second-half football for the deadlock to be broken and it went to the hosts.
Jacobson's delivery was expert from the inswinging corner and Onyedinma was there to crash home a header from close range.
Rovers went in search of a response, but Ben Brereton slammed wide under pressure from Jack Grimmer and Jason McCarthy.
Rovers were struggling to find a route towards goal, with Taylor Harwood-Bellis glancing a header down and over Stockdale's crossbar as the clock ticked into the final 10 minutes in Buckinghamshire.
The visitors continued to probe though and Rothwell's dancing feet worked a yard in the box before seeing Stockdale in his way with just two minutes remaining, and then substitute John Buckley thumped an effort wide.
That was to be the last action from what was a disappointing afternoon in Buckinghamshire.
Rovers return to action on Monday afternoon when AFC Bournemouth visit Ewood Park, kick-off 3pm.
Wycombe Wanderers: Stockdale, Grimmer, Jacobson (c), Gape (Adeniran, 16) Ikpeazu (Akinfenwa, 90), Knight, Muskwe (Samuel, 90), Thompson, Onyedinma, McCarthy, Mehmeti (Horgan, 84).
Unused substitutes: Allsop. Stewart, Kashket, McCleary.
Goal: Onyedinma, 47.
Booked: Thompson, 85
Rovers: Kaminski, Rankin-Costello (Nyambe, 42), Lenihan (c), Harwood-Bellis, Douglas, Trybull (Buckley, 72), Holtby (Downing, 57), Rothwell, Brereton (Dolan, 57), Gallagher, Elliott (Johnson, 72).
Unused substitutes: Pears, Bell, Evans, Branthwaite.
Booked: Holtby, 26.
Referee: David Webb.