The visitors were awarded a free kick in the 21st minute after Marc McAusland was found to have handled the ball, allowing Richard Brittain to fire in the kick from just outside the penalty area to give Ross County the lead.
County continued to look the brighter of the two sides throughout the opening 45 minutes, but could not add to their lead before the break.
The home side hit back at the start of the second half, Steven Thompson with a close-range effort.
County looked to get their lead back straight away, Rocco Quinn and Sproule both pushing up front.
Their efforts were rewarded in the 66th minute, Sam Morrow slotting the ball in from inside the penalty area.
Sproule added to the lead with a quick-fire brace, netting twice in four minutes to put County three goals ahead.
The first of the Northern Irishman's goals came from outside the box, before he added a second after a Quinn strike was parried back into play by St Mirren keeper Craig Samson.
The win means that County are just one point behind St Mirren in the Scottish Premier League table.