Unfortunately, the Barrfields side were hit with late injuries to both midfielders Matt Bennett and Gary Fleming before kick-off.
It was a bright opening from Largs as they took the game to Rob Roy in the early stages, and had some decent openings.
But Rob Roy were looking dangerous going forward and had the ball in the back of the net on 15 minutes
Gallagher's roving run into the box, cutting in from the left, resulted in a pinpoint cross to Watt who sidefooted home, but the offside flag was raised.
Thistle responded with a spectacular move and James Marks overhead kick had power but the keeper was well positioned to make the save.
The ever industrious Laurie McMaster was having a good game, and even when he lost possession, scurried back and managed to make amends to clear.
Experienced defending from Walton denied Watt breaking through, and Largs were pushing forward on the break - the best chance fell to Marks who screwed a powerful volley wide of target.
Thistle keeper Ross Lundy made a fantastic one handed save at full stretch to tip a curling shot over the bar as the visitors increased the pressure.
Rob Roy notched the opener on 43 minutes, and it was a clever back heel flick from Chris Duff after a free kick, which looped into the net. There were some angry scenes as both teams headed to the dressing room. 
And the Kirkintilloch side quickly added to their lead after the break.
There was some head tennis in the Thistle box which left McCall with a simple job of nodding home from a few yards out.
Largs hit back quickly - it was McMaster who raced on to the box following a one-two with James Marks, but the young wing-back was chopped down, and the ref pointed to the spot. Sub Glenn Thomson showed composure to knock the ball home and half the deficit on 57 minutes.

Largs and Millport Weekly News:

James Marks managed to peel away from a defender on the left but blazed a shot across the face of goal.
And Robert Love nearly managed to get the leveller as he turned in a dangerous cross but the Rabs keeper managed to block, and it went out for what should have been a corner.
It was a narrow defeat for Largs in a match they could ill afford to lose in their battle for survival in the top flight.
Largs: Lundy, Fisher, Little, Walton, Gilbride, McDonald, Tennent, Struthers, Marks, Love, McMaster. Subs: Thomson, Ashe, McWatters, Little, Graham (GK).
Rob Roy: Brown, McCall, McKenzie, Green, Buchanan, Whelan, Gallagher, Pearson, Watt.