The former Huddersfield defender won the man-of-the-match award as Walsall scored six for the first time in a league game at their 20-year-old stadium in their first win in six matches.
New striker Jason Price, on loan from Carlisle, missed a chance for Walsall before Butler opened the scoring with a header from Matt Richards' free-kick.
Rovers missed a couple of reasonable opportunities to draw level before Walsall increased their lead in the 34th minute when Mathew Gill, on loan from Norwich, drove in a flick from Jon Macken and a minute from half time Julian Gray made it three with a cracking volley following a corner.
Rovers made a couple of changes at half-time and one of the subs, Scott Davies, set up Jeff Hughes to pull one back in the 48th minute, but two minutes later their hopes were dashed when Richards notched his eighth of the season with a 25-yard drive.
Alex Nicholls volleyed number five from Macken's pass and Butler completed the rout with a header from Gill's corner in the 73rd minute.