The home side had most of the ball, however shots on goal were even with eight apiece.
Frosinone went close early with Luca Moro’s close-range shot hitting the crossbar.
Goalkeeper Stefano Turati scared the home crowd when he spilled a shot from distance, before picking up his own crumbs.
Sergio Kalaj was lucky to stay on the pitch after his second-half studs-up challenge on Cosenza’s Massimo Zilli was only given a yellow card.
The later winner came courtesy of Marco Brescianini’s curling effort from just outside the ‘D’.
Frosinone are still six points clear of second-placed Genoa, while Cosenza are one point from safety.
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