The 42-year-old finished two shots ahead of Ireland's Padraig Harrington to claim his first European Tour win for two years and the pounds 41,000 first prize.
But the popular Italian knows he can not afford to rest on his laurels with the final qualifying event for the Ryder Cup just three days away.
"It's better not thinking about the win now because I still have to win next week," said Rocca, who must finish in the top two at the BMW International Open in Munich to have a chance of qualifying automatically for the European team.
"I can't relax. I think I need to win in Munich and even that may not be good enough but my game is good and I have a chance. I got the job done and that's what I wanted to do this week. I tried to stay concentrated because with the wind the course is tricky and you can make a 65 or 76 here."
Rocca began the day tied for the lead with Harrington, who himself can still make the European side to defend the trophy in Boston in September.
At one stage Rocca held a three shot lead after a trio of early birdies before a similar run of bogeys saw Harrington, cheered on by the home crowds, level with three holes to play.
The key moment then came on the par-five 16th, a good birdie opportunity, where Harrington's drive went out of bounds, costing the Dubliner a bogey six and giving Rocca a one shot lead.
With Rocca 30 feet away from the hole on the 18th there was still hope for Harrington but Rocca finished in style, holing for a birdie three to card a final round 70 and 12 under total of 276.
Harrington finished alone in second place to boost his chances of qualifying for the Ryder Cup, with England's Gary Evans a shot further back in a tie for third on nine under after a level-par 72 alongside Paul Broadhurst and Ireland's Des Smyth.
"I don't think it was destined to be," said a disappointed Harrington who just missed out on qualifying for the Ryder Cup team in 1997.
"My concentration was poor and the greens felt very quick and that destroyed my ability to hit putts with any confidence.
"I hit it all over the place off the tee and paid the penalty for hitting too many loose shots. I was no more nervous than any other time but I need to improve my focus."
If Rocca fails to qualify automatically, he may well still figure in the team as one of captain Mark James's two wild card selections which will complete the team for Brookline.
He has played in the last three competitions, famously beating world No 1 Tiger Woods four and two in the singles in Valderrama, and with a number of rookies guaranteed to be in the side, his experience could persuade James to pick him for the team.
"If Mark thinks my game can help the team, and I've stayed in good shape even if I don't make it, if he needs me I'm here. I'd be very happy to play."
WEST OF IRELAND CLASSIC (Galway) Leading final-round scores and totals (GB or Irl unless stated): 276 C Rocca (It) 70 68 68 70. 278 P Harrington 69 69 68 72. 279 P Broadhurst 73 66 72 68; G Evans 70 66 71 72; Des Smyth 71 68 69 71. 280 M Long (NZ) 69 72 73 66; A Hansen (Den) 67 74 71 68; P McGinley 68 69 74 69; G Emerson 68 71 72 69. 281 M Hallberg (Swe) 70 71 71 69. 282 A Raitt 68 75 66 73. 283 K Storegaard (Den) 68 71 74 70; E Boult (NZ) 66 75 71 71; S Hansen (Den) 67 72 72 72; E Carlberg (Swe) 68 67 74 74. 284 B Teilleria (Fr) 70 72 72 70; M Lafeber (Neth) 71 68 73 72. 285 P Lawrie 70 76 72 67; Bradley Dredge 69 71 76 69; A Oldcorn 68 76 71 70; A Butterfield 71 70 72 72; F Henge (Swe) 70 70 71 74.Reuse content