The Blades' homegrown midfielder struck in the 50th minute, capitalising on a rare good delivery from Keith Gillespie to give his side victory and spare the blushes of manager Neil Warnock.
The game began in scrappy fashion with neither side able to impose themselves on a decidedly low-key affair.
A frustrated Alan Quinn blazed a right-footed strike from 35 yards over the bar as early as the seventh minute but it was not until twenty minutes later that visiting keeper Nathan Abbey was even tested.
Blades midfielder Paul Ifill forced Abbey into action with a fearsome drive from 30 yards which was tipped round the post.
Ifill was then guilty of a foul on Boston defender Alan White as the Pilgrims proved tough for the Championship side to break down.
Pressure from the home side finally told early in the second half - much to the relief of the Bramall Lane crowd.
Winger Gillespie won a corner and from his cross Ross hammered home from inside the penalty box to give his side victory.
Chris Armstrong should then have doubled the advantage but was wasteful when presented with the chance to shoot inside the box before Ifill was unlucky to see a good effort from the edge of the box parried to safety by Abbey.