Former Wales international Saunders was a whirlwind replacement for Sean O'Driscoll following his surprise sacking last week, and quickly oversaw a fortuitous 1-0 win over Crystal Palace that ended Rovers' 19-game winless streak.
They had looked like they were set for a return to type tonight, though, when England Under-21 striker Martyn Waghorn scored his first goal for Hull following a Neil Sullivan error to give the Tigers a deserved half-time lead.
But after some words from Saunders Rovers improved after the break and Gillett's goal ensured they avoided worsening the start they made to the 1997-98 season - a campaign that resulted in relegation from the Football League.
Going down would not have such dire implications this time around, but a four-point haul from Saunders' first two games in charge suggests they could soon be out of danger - especially if loan striker Jon Parkin continues to impress.
The former Hull man was hugely disappointing in the first half, but began to put his renowned burly frame to good use in the second and almost bullied Hull into conceding Gillett's goal - a strike he laid on in front of the watching Pascal Chimbonda, who is talking to Doncaster about a possible move.
The former Tottenham man will not have enjoyed the first 45 minutes, though, as Waghorn stole the show.
He scored 12 goals during a successful spell under Pearson at Leicester two seasons ago and, although the former Sunderland trainee had not netted for Hull prior to tonight, his form had been impressive, none more so than when scoring in back-to-back appearances for his country.
His confidence was evident early on here as he teed-up Robbie Brady for a shot Sullivan held, before he nearly opened the scoring in the 13th minute.
Tom Cairney's pass split Doncaster's pedestrian centre-half pairing of Shelton Martis and Richard Naylor and found Waghorn, whose shot through Sullivan's legs appeared to be easing over the line until James O'Connor appeared to clear it.
Doncaster were offering little, with James Coppinger having their two best chances of the opening half.
First he warmed Adriano Basso's palms with a low free-kick which caught the wall, before he failed to make the most of the space afforded to him after he latched on to George Friend's long ball.
Much of the passing game that Doncaster were known for under O'Driscoll was absent too and it was no more than Hull deserved when they took the lead just after the halfway point of the opening half.
Fryatt's run took him past O'Connor and, after Sullivan failed to take his cross, Waghorn's run into the box allowed him to bundle the unexpectedly loose ball into an open net.
Neither side went close to scoring for the rest of the half, but Hull could twice have added a second early after the break had the lively Brady produced a better final ball after spinning Friend.
Until that point, Parkin had struggled up front in his second came for the home side, but finally imposed himself on the game in the 57th minute.
The home side had hardly been building pressure, but when Parkin nodded Friend's cross across the six-yard box, Gillett was waiting to drill a precise effort beyond Basso and level the scores.
Hull's defence - one of the meanest in the league with just six goals conceded before tonight - was now looking ruffled, especially by Parkin, who nearly played in substitute Billy Sharp and was then booked for taking the wind out of Joe Dudgeon.
Parkin's lob then gave Basso a routine save under his bar minutes after Brady's feet worked himself an opening that he failed to take, but despite a number of loose balls bouncing in both boxes, there were no more chances of note.